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Full text of "Plant disease and pest control"

UNIVERSITY OF CALIFORNIA 

COLLEGE OF AGRICULTURE 

AGRICULTURAL EXPERIMENT STATION 

CIRCULAR No. 265 
June, 1923 

PLANT DISEASE AND PEST CONTROL 

BY 

W. T. HOENE, E. O. ESSIG and W. B. HEKMS 



TABLE OF CONTENTS 

Diseases and insect pests of crops, alfalfa to walnut 1-51 

General subjects (troubles of many crops) 53-60 

Household pests and animal parasites 60-69 

Formulas 70-96 



ALFALFA 

Crown Wart, Urophlyctis alfalfas (Lag.) Magn. — Crown wart 
was formerly called crown gall, but is not connected with true crown 
gall (see general subjects, p. 55). Rounded irregular tumors develop 
near the surface of the ground and some plants may subsequently 
die. Widely distributed, but not often destructive in California. 

Dodder or Love Vine, Cuscuta sp. — Yellowish threads grow up 
and entwine the plants, causing serious injury. This is a parasitic 
plant with minute flowers and with seeds similar in size to alfalfa seeds. 
Avoid seed in which dodder occurs. The State Department of Agri- 
culture, Sacramento, maintains a laboratory for testing seeds, to 
which samples may be sent. Small patches may be killed by mowing 
and, when dry, burning with additional material or kerosene. After- 
wards resow the spot. Badly infested fields should be plowed up. 
In the drier sections it is reported that dodder may be killed by keep- 
ing the field dry for a time, as alfalfa will endure more drought than 
dodder. 

Downy Mildew, Peronospora trifoliorum De Bary. — Upper leaves 
become partly yellow with the edges turned down. The lower sides 
of the leaves have a fuzz which turns violet. Very common in winter 
and spring. Not destructive. 



Z UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 

Leaf Spot, Pseudopeziza medicaginis (Lib.) Sacc. — Small dark 
spots appear on the leaves, which fade and drop early if spots are 
numerous. The commonest and most universal trouble of alfalfa 
in California. Favored by moist atmosphere, and worst on weak 
plants in dry soils under unfavorable growing conditions. Fre- 
quently causes loss of nearly all the leaves. Normally disappears 
after cutting and good irrigation. 

Rust, Uromyces striatus Schr. — Powdery dark brown dots appear 
on the leaves. 

Stem Rot or Wilt, Sclerotinia libertiana Fcl. — Stem rot is caused 
by the same fungus as cottony rot of lemons, green rot of apricots, 
fig die back, etc. Vetch and various leguminous cover crops are 
attacked. Moist weather favors it. Stems rot off near the surface 
of the ground and the affected part becomes covered with a cottony 
snow-white mold. Irregular black bodies as large as popcorn grains 
form in protected places about and in the diseased stems. 

Treatment of foliage diseases of alfalfa in California has gen- 
erally been confined to mowing the diseased stand and applying 
water if that is needed. Sometimes the ground is disked or treated 
with a renovator. Early mowing may dispose of a diseased and weedy 
crop which may be used for silage, or if too bad for this purpose, 
such a crop makes good orchard mulch. Where the stand becomes 
too thin or uneven, it should be plowed up and resown. Perhaps 
no crop is more dependent on proper soil preparation and treat- 
ment. Consult your local farm advisor, or write to the University 
of California, College of Agriculture. 

Alfalfa Caterpillar, Eurymus eury theme (Boisd.). — The caterpil- 
lars are about one inch long and dark green in color with a distinct 
and often a pale white or yellow line on each side. They feed on the 
leaves and may entirely defoliate the plants. The yellow butterflies 
may be seen in great numbers hovering over the fields. Cutting as 
soon as the caterpillars appear in destructive numbers, followed by 
irrigation, is the best method of control. 

Armyworms, Cutworms, Grasshoppers, etc. — See "General Sub- 
jects," p. 53. 

Clover Seed Chalcis (Bruchophagus funebris How.). — The small 
white larv f a of this insect is just large enough to fill the seed. It 
occurs in sufficient numbers to greatly reduce the seed crop in most 
localities in the state. Destroying all the seed heads during winter 
and the straw after threshing will greatly reduce the infestation for 
the next year. 



Circular 265] PLANT DISEASE AND PEST CONTROL 3 

ALMOND 

Armillaria, Crown Gall, Sour Sap. — See "General Subjects." 

Rust, Transclielia punctata (Pers.) Arih.=Puccinia pruni. — Pow- 
dery dark brown dots appear on the leaves in summer and autumn. 
Also on prune, plum, peach, and apricot. No control is known. 

Shot-hole, Coryneum beijerinckii Oud. — Principally due to peach 
blight fungus. Small spots are killed on the young rapidly expand- 
ing leaves, the living part draws away from the dead area and the 
latter drops out. Young fruits are also attacked and may drop. 
There may be much injury and loss both of fruit and foliage. Spray 
with lime-sulfur 1-10 just as the buds are swelling. 

Unfruitfulness. — Usually due to frost or to rain at blooming 
time, or to lack of a suitable mixture of varieties for cross pollination 
(most varieties are self -sterile), or to the lack of bees for carrying 
pollen, or to weakness from red spider or other injury the previous 
year. The selection of suitable soils and thermal belt situations 
offer some difficult problems for the almond. See "Frost" under 
"General Subjects," p. 55. 

California Peach Borer. — See "Peach." 

Peach Twig Borer.— See "Peach." 

Red Humped Caterpillar. — See ' ' Prune. ' ' 

Red Spider or Almond Mite, Bryobia praetiosa Koch. — The 
largest orchard mite, nearly the size of a pinhead ; brownish or green- 
ish with reddish legs, the front pair as long as the body and much 
longer than the other legs. The bright red, globular eggs are laid in 
great numbers on the limbs and twigs of the trees, where they remain 
through the winter and hatch in the spring. Spray the trees in 
the winter (January and February) with lime-sulfur 1-10 or crude 
oil emulsion (Formula 18) to destroy the eggs. To control the mite 
during the growing period of the trees apply dry sulfur, sulfur 
paste, wettable sulfur sprays (Formula 13 or 14), or lime-sulfur 
1-50 plus 5 pounds of wettable sulfur as soon as the mites appear 
in the spring and as often as necessary during the summer and fall. 
(See Bull. No. 347.) 

San Jose Scale. — See "Apple." 



4 university of california experiment station 

Combined Spraying 

Lime-sulfur spraying when the buds are swelling will control shot- 
hole fungus and peach twig borer, and help to destroy San Jose scale 
and the eggs of the almond mite. Crude oil emulsions will also 
destroy scale insects, almond mite eggs, and will arrest some of the 
fungus diseases when applied as a dormant spray. 

APPLE 

Blight, Bacillus amylovorus (Burr.) De T. — See "Pear." Re- 
move all worthless apple, pear, and quince trees near apple or pear 
orchards. Christmas berry, Cotoneaster, loquat, and related wild 
or ornamental plants should be watched for blight. See ' ' Pear. ' ' 

Mildew, Sphaerotheca leucotricha (E. & E.) Salm. & S. oxyacan- 
thae (De C.) De B. — A white powdery growth covers leaves and 
shoots, causing stoppage of growth and distortion. Where abundant 
the tree is weakened. Especially serious in foggy sections. Cut 
out mildewed twigs as thoroughly as possible in winter. Use lime- 
sulfur for scab spraying (See "scab") or, if scab is not serious, use 
sulfur paste, 16 pounds to 200 gallons of water (or home-made 
wettable sulfur spray, Formula 13 or 14) when petals are falling. 
Later spraying for mildew may be done with the same material. 
Sulfur sprays cause injury to apple trees in some sections. 

Sappy Bark, Polystictus versicolor (L.) Fr. — Bark puffs up in 
winter about wounds and dries out later, becoming loose and papery. 
Recurs in succeeding winters, causing death of limbs and general 
breakdown of trees. Caused by wood decay in the interior of the 
tree. Avoid large wounds or protect them with a covering of asphalt. 
See "Wood Decay" under "General Subjects." 

Scab, Venturia inequalis (Cke.) Wint. — Fusicladium. — Velvety 
dark moldy patches on young fruit and sometimes on leaves and 
twigs, rough corky spots on mature fruit, with distortion. Spray 
with Bordeaux mixture (Formula 9) or lime-sulfur 1-20, just as 
winter buds open. Again with lime-sulfur 1-35 when petals are 
falling. Bordeaux applied after the bloom may russet the fruit. 

Codling Moth, Cydia pomonella (Linn.). — The common white or 
pinkish worm or caterpillar nearly one inch long is found inside 
the fruit. For control, spray from two to five times as needed. First 
spray should be applied as the petals are falling, using 2y 2 pounds 
powdered or 5 pounds paste arsenate of lead to 100 gallons of water ; 



Circular 265] PLANT DISEASE AND PEST CONTROL 5 

the second spraying should be made three weeks later using the 
same strength. The remaining applications should follow as needed, 
but should be somewhat weaker, 2 pounds of powdered or 4 pounds 
of paste arsenate of lead to 100 gallons of water. Cover with a fine, 
fog-like spray. For a spreader use 1 pound of dry casenite or bill- 
board paste to 100 gallons of spray material. Also see " spreaders" 
under "General Subjects." 

Flat-headed Apple Tree Borer, Chrysobothris mali Horn. — The 
full-grown larvae or borers are white or pale yellow and vary from 
one-half to three-quarters of an inch in length. The portion just 
behind the head is greatly enlarged and flattened, a character which 
is responsible for the common name. The adult beetles lay eggs on 
sunburned or other dead areas of the trunk. Whitewash trunks to 
prevent sunburn and repel egg-laying. Avoid injuries and wounds. 
Dig out borers and paint with asphaltum. 

Fruit Tree Leaf Roller, Archips ■ argyrospila Walker. — The eggs 
are laid in small, flat, grayish or brownish masses, usually on the new 
growth near the tops of the trees, in the fall. They hatch in the 
spring and the caterpillars draw the leaves together into compact 
rolls in which they live, and from which they wriggle violently if 
disturbed. When mature the larvae are nearly three-quarters of 
an inch long, deep green, with the head and thoracic shield dark 
brown or black. The most satisfactory means of control is directed 
against the eggs, and consists in the use of a miscible oil or crude 
oil spray (Formula 18) during the winter. Great care must be 
taken to thoroughly drench the limbs and particularly the tops and 
outside branches. Some relief may be had during the summer by 
spraying with 2 pounds of powdered or 4 pounds of paste basic 
arsenate of lead to 100 gallons of water. 

Green and Rosy Apple Aphis, Aphis pomi DeGeer and Anura- 
phis roseus Baker. — Both of these aphids are easily distinguished by 
their color and the characteristic curling of the leaves caused by 
their method of attack. Control measures are difficult and must be 
thorough to secure satisfactorj' results. Late dormant lime-sulfur, 
1-10, applied just before the buds open, gives fair results in killing 
the eggs, but it is better to spray from the time of the bursting of 
the buds until the leaf buds are one-half inch long with nicotine 
and soap (Formula 27), or with nicotine and distillate emulsion or 
miscible oil (Formula 24), or to dust thoroughly with 5 or 6 per 
cent nicodust. At this time the young stem-mothers may be de- 
stroyed as they hatch from the eggs. 



6 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION 

Red Humped Caterpillar. — See ' ' Prune. ' ' 

San Jose Scale, Aspidiotus perniciosus Comst. ; Oyster Shell Scale, 
Lepidosaphes ulmi (Linn.) ; and Other Scale Insects.— The scales of 
the first are circular and gray, while those of the second are oyster- 
shaped and similar in color. They occur on all parts of the tree, the 
first causing a red or purplish stain on the bark and fruit. For the 
San Jose scale alone, spray with lime-sulfur, 1-10, during the winter 
months. For a mixed infection of scales, spray preferably with crude 
oil emulsion (Formula 18), or with distillate emulsion (Formulas 
21-23), or with miscible oil. The lighter oil sprays are not so effi- 
cient as the crude oil emulsion. 

Tent Caterpillars and Cankerworms. — See "General Subjects.'' 

Tussock Moths, Hemerocampa vetusta (Boisd.) and Notolophus 
aniiqua (Linn.). — The caterpillars are brilliantly colored and clothed 
with tufts of white hair on the dorsum, with a single long black tuft 
at the rear and two in front, the latter being responsible for the 
name "horn worms." The eggs appear as white flat felty masses 
on the old cocoons and on the limbs of the trees. They are deposited 
in late summer and fall, but do not hatch until the following spring. 
The female moths are wingless, while the males are normally winged. 
Control by removing the egg masses during the winter months. Great 
numbers of the caterpillars may be jarred from the trees and their 
reascending prevented by applying a band of cotton, wire screen, or 
tanglefoot around the trunks. Poison sprays are of little use. 

Woolly Apple Aphis, Eriosoma lanigera (Hausm.). — Easily dis- 
tinguished by the reddish bodies completely covered with white 
woolly wax. During the winter months spray with distillate emul- 
sion (Formula 23), miscible oil, or carbolic acid and distillate emul- 
sion (Formula 26a). For the root form, expose the crown of the 
roots and pour in 4 or 5 gallons of any of the above spray mixtures 
and recover the roots. Nicotine sulfate (Formula 27) is also effec- 
tive, or refuse tobacco stems or leaves may be buried in the soil over 
the main roots during the rainy season. Use para-dichlorobenzene dur- 
ing the fall. Delicious and Northern Spy rootstocks are somewhat 
immune and are often used to repel serious attacks of this pest. Of 
the two stocks the former is more vigorous and easily grafted. 

Combined Spraying 

1. For serious infestations of scale insects, for removal of moss or 
lichens, and for a general clean-up, use lime-sulfur 1-10 or crude oil 
emulsion (Formula 18) during the winter. 



Circular 265] PLANT DISEASE AND PEST CONTROL 7 

2. For green, rosy, and woolly aphis, use distillate emulsion (Form- 
ula 23) or miscible oils just as the buds are beginning to open. If 
only the first two are present and scab is a serious pest, substitute 
late dormant lime-sulfur 1-10. This will assist in the control of the 
San Jose scale, if present. Combinations of oil sprays for insects 
with lime-sulfur or Bordeaux mixture for fungous diseases are not 
considered advisable. 

3. For codling moth and scab use 2 pounds powdered or 4 pounds 
paste basic arsenate of lead to 100 gallons of 1-35 lime-sulfur when 
petals are falling. For mildew, add 8 pounds of sulfur paste to each 
100 gallons of the above and one-half pint of 40 per cent nicotine 
sulfate for green or rosy aphis. For later infestations of codling 
moth and scab, repeat above, following recommendations for mildew 
and aphis if these need attention. 

In large apple-growing districts obtain advice of local horticul- 
tural authorities for modifications of the above. 

4. For summer infestations of aphis and red spiders, a combined 
nicotine and sulfur dust may be applied to great advantage. 

APRICOT 

Armillaria, Crown Gall, Sour Sap, Wood Decay. — See " General 
Subjects," p. 53. 

Bacterial Gummosis, Bacterium cerasi Griffin. — Active during 
moist weather of winter and spring. Attacks buds, twigs, branches, 
trunks, and succulent young shoots. On the last there is a killing 
and blackening of tissue, at first superficial but often killing the shoot. 
Copious turbid or colored gum appears. Affected bark when cut 
into shows moist gumming rot. Cut out diseased bark and disinfect 
wounds and tools as for pear blight. (See "Pear"). After the 
first rains, the orchard should be frequently inspected and all cankers 
treated promptly to stop their spreading. Summer treatment is 
of doubtful value in controlling the trouble, but trees should be 
repaired to prevent wood decay. (See "General Subjects," p. 58.) 
Appears to be increasing in severity. No remedy is known for the 
phases on buds, twigs and succulent growth in early spring. A heavy 
Bordeaux spray before the rains begin as for peach blight, may 
help. 

Black Heart. — Certain branches die back suddenly in summer 
with leaves attached and the wood of affected twigs becomes dark- 
streaked far back into the tree. Peaches, prunes, and almonds are 



8 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 

sometimes affected. Avoid excessive irrigation, severe cutting back, 
or otherwise promoting too succulent growth. Make conditions as 
normal as possible ; trees usually outgrow the trouble. A publication 
on this subject is soon to appear. 

Brown Rot, or Monilia Brown Rot, Monilia Blossom Blight, Gum- 
ming Twig Blight and Monilia Rot of Ripe Fruit, Sclerotinia cine- 
rea (Bon.) Schrot. {Sclerotinia fructigena or Monilia fructingena 
in earlier works in America). — The brown rot fungus is active only 
in moist weather, but may then be very destructive. Flowers are 
susceptible when the white petals show in the buds and remain so until 
the ''jackets" (calyxes and other flower parts) are shed from the 
fruit. The fungus grows down through the flower or fruit, caus- 
ing it to rot, usually without falling, and penetrates into the spur 
or twig for several inches. Inner bark and wood turn brown and 
copious amber gum appears. Long shoots may be killed by girdling 
from a spur. Ripening fruit is attacked (usually in injuries) and 
rots, becoming covered with dusty gray powder. If allowed to dry 
out the rotted fruit becomes a tough "mummy," often hanging in 
the tree over winter. Where fruits are crowded, whole clusters 
frequently are lost. 

The fungus remains alive in mummies and dead twigs and forms 
spores during wet weather of winter and spring. All stone fruits 
and almonds are attacked. The Madeline pear is very susceptible. 

After the crop is off, or at any time during fall or winter, remove 
all mummies and dead twigs and plow them under, bury deeply or 
burn. Where the disease is serious, spray with Bordeaux 8-8-50 in 
the red bud stage (just before the white petals show). Or if very 
bad spray several times in quick succession, continuing up to full 
bloom. For the fruit rot Bordeaux 4-5-50 may be used up to the 
time when it will remain and be unsightly on the fruit — perhaps two 
months before ripening. Lime sulfur is efficient in case of brown 
rot, but has frequently caused "sulphur sickness' in apricot trees, 
and is not recommended. Sulfur sickness has appeared as yellowing 
of foliage, stunting of fruit, and failure of trees to bloom normally 
the following year. 

Bud Blight, Shot Hole, Fruit Spot, Peach Blight, Coryneum oeije- 
rinckii Oud. — Buds are blackened and killed during winter; spots 
killed in the opening leaves fall out and leave holes, and small red 
spots with light centers are formed in the young fruit. Spray with 
Bordeaux or lime-sulfur between November 15 and December 15, and 
repeat in spring when buds are showing pink. See "Almond" and 
"Peach." Destructive in interior valleys and foothills. 



Circular 265] PLANT DISEASE AND PEST CONTROL 9 

Frost Scabs, Fruit Cracking and Red Specking, Failure of Flower 
Buds to Open on Strong Shoots, Unfruitfulness of Some Varieties. — 

Due to climate or obscure causes, and often confused with fungus 
diseases. 

Green Rot and Twig Blight, Sclerotinia libertiana Fcl. — Often 
associated with brown rot and confused with it. Where the fungus 
shows on the surface it is snow white instead of gray as in brown 
rot, and sclerotia may sometimes be found. (See "Stem Rot" of 
"Alfalfa," "Lemon Rot," etc.). Does not affect the ripening fruit. 
Control is not developed, but sprays for brown rot should be of some 
value. 

RUST, Transchelia punctata (Pers.) Arth. = Puccinia pruni. — 
Sometimes causes small hard points in the skin of the fruit, resem- 
bling "fruit spot" above. Also rarely there has been severe drop- 
ping of young leaves in early summer following very heavy infection. 
Early infection apparently came from old rusted leaves which hung 
on the trees over winter. If this trouble should persist, it would 
probably be desirable to bring down the old leaves during winter by 
means of a caustic spray or otherwise. See "Almond," "Peach," 
"Plum." 

Scab, Cladosporium carpophylum Thum. — Sooty patches to one- 
half inch in diameter and often confluent form on the fruit, causing 
drying and cracking. Sprays for brown rot will probably control this, 
but if not effective, additional sprays after full bloom should be tried, 
using Bordeaux (Formula 9, p. 74). 

Branch and Twig Borer, Polycaon confertus Lee. — A small elong- 
ated brown beetle, one-quarter of an inch long, which bores clean 
round holes at the bases of buds, fruit spurs, and in the forks of small 
twigs. Often makes severe pruning necessary. The insect breeds in 
dead oaks and prunings of fruit and other trees. Clean up and burn 
dead brush and prunings around orchards. 

Brown Apricot Scale, Lecanium corni Bouche, and Black Scale, 
Saissetia oleae (Bern.). — Immature scales of both species are brown 
or grayish, the latter having a distinct "H" on the back. They 
mature in May and June and are nearly hemispherical; the former 
is smooth and brown and the latter black. Control is directed against 
the immature winter forms which occur on the new growth. Spray 
the trees when dormant, December to February, with crude oil emul- 
sion (Formula 18), distillate emulsions (Formulas 20-23), and mis- 
cible oils, all of which give excellent control for both of these scales. 
Thoroughness of application is necessary. (See Circular No. 224, 
Calif. Agr. Exp. Sta., Univ. Calif., Dec, 1920.) 



10 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION 

California Peach Borer. — See "Peach." 

Cankerworms. — See "General Subjects." 

Fruit Tree Leaf Roller.— See "Apple." 

Peach Twig Borer.— See "Peach." 

Red Humped Caterpillar. — See "Prune." 

Shot Hole Borer, Xyleborus xylographies Say and Bark Beetle, 
Eccoptog aster rugulosus (Ratz.). — Very small beetles boring into the 
sapwood and heartwood of various fruit trees, preferring usually 
those not in the best of health. White larvae of the latter may be 
found during the winter months in sapwood, where they may en- 
tirely girdle the trees. Keep the trees growing vigorously; prune 
out and burn all dead wood; destroy all infested branches imme- 
diately. 

Combined Spraying 

Lime sulfur 1 to 10, applied as the buds are beginning to open, 
will control peach twig borer, remove moss and give the trees a gen- 
eral clean up, but this may cause sulfur sickness. (See "Brown 
Rot.") General clean up may be accomplished by a dormant spray 
of crude oil emulsion (Formula 18, p. 82) or miscible oil (p. 85), and 
peach twig borer may be controlled by adding basic arsenate of 
lead powder, 3 lbs. to 200 gals, of Bordeaux mixture, in spring, to 
control broAvn rot or bud blight and fruit spot. See also "Twig 
Borer ' ' under ' ' Peach. ' ' 

ARTICHOKE 

Artichoke Plume Moth, Platyptilia carduidactxjla (Riley). — This 
moth is brown with narrow wings and one inch long. The caterpillars 
are less than one inch long, yellowish with black heads. They feed 
chiefly upon the developing heads of the artichoke, making deep 
tunnels or eating through the bracts. Their work is often very destruc- 
tive and considerable loss occurs every spring because of it. 

Field sanitation is one of the best means of control. Infested 
heads should be removed at every picking and burned. Burning or 
deep plowing should be practiced to dispose of the old plants after 
cutting in May and June. Thistles and deserted or wild artichoke 
plants should be promptly destroyed to eliminate breeding places. 
Dusting with 5 per cent nicodust or with a combination of 5 per 
cent nicodust to which 1 pound of powdered arsenate of lead is 
added to every 4 pounds of the nicodust is recommended after each 
picking, until the attacks are reduced to a minimum. 



Circular 265] plant disease and pest control 11 

Artichoke Aphis, Myzus braggii Gill. — A green and black aphis 
©ften in immense numbers on the heads and the undersides of the 
leaves. Dust with 5 per cent nicodust or spray with nicotine, sulfate 
and soap (Formula 27.) 

ASPARAGUS 

Rust, Puccinia asparagi D. C. — Minute yellowish blisters or sori 
appear on leaves and stems; these rupture and become rust-colored 
and dusty and later black. Plants become pale and bare and are 
much weakened for succeeding crops. Keep down all volunteer 
growth in and about the fields. Burn all old growth after it dies 
down and cultivate all surfaces well before new growth comes up. 
After cutting stops, irrigate and cultivate to secure vigorous growth, 
and in about three weeks dust with sulfur while the dew is on, or 
spray with resin-Bordeaux (Formula 10a, p. 75) or lime-sulfur 
containing fish-oil soap for a spreader, or with fish-oil soap followed 
by dusting with sulfur while still wet. Repeat once or twice, accord- 
ing to the severity of the disease in the vicinity. For young fields, 
dust repeatedly with sulfur as above to prevent infection, beginning 
when the tops first fully feather out. 

Asparagus Beetle, Crioceris asparagi Linn. — The beetles are slen- 
der, one-fourth of an inch long, metallic blue-black with red and 
yellow markings. The larvae are dull brown or olive green with 
black head and legs. They feed in great numbers upon the seed- 
lings. Control by clean culture, by cutting and burning seedlings, 
or by spraying them with nicotine soap spray (Formula 24 or 27.) 
A 6 per cent nicodust also gives quite efficient control. 

Garden Centipede, Scutigerella calif arnica (Woodw.). — These are 
small, white, centipede-like animals, scarcely more than one-quarter 
of an inch long. They live in the damp soil in great numbers and 
often seriously damage the young asparagus tips before they reach 
the surface of the soil. Clean culture, winter flooding, and crop 
rotation are the best control suggestions. 

AVOCADO 

Pythiacystis Canker, Pythiacystis citrophthora S. & S. — Limb and 
trunk cankers, resembling gummosis of lemon, but the gummy exu- 
date hardens into a granular whitish mass. Treat as for citrus gum- 
mosis. See ("Citrus Fruits"). 



12 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 

Soil or Water Injury. — Certain sickly conditions apparently 
caused by uneven moisture due to hardpan or other soil defects. 
Trees apparently are sensitive to waterlogging of soil and have poor 
recuperative power after such injury. 

Branch and Twig Borer. — See "Apricot." Sap collecting in the 
burrows produces, on evaporation, white powdery masses over the 
entrances, completely concealing them. 

Fruit Tree Bark Beetle.— See "Apricot." 

Spanish Red Scale, Chrysomphalus dictyospermi Morgan. — A pale 
brown, circular scale, infesting all parts of the tree and serious in 
greenhouses, but as yet not adapted to orchard conditions. Control 
by fumigation with hydrocyanic acid gas. 

Thrips : Bean Thrips, Heliothrips fasciatus Perg., and Greenhouse 
Thrips, Heliothrips haemorrhoidalis Bouche. — See "Prune." These 
insects attack the leaves and fruit, causing a shiny, hard discolored 
surface which has a tendency to check, or crack, and which is covered 
with numerous fine specks of excrement. 

BARLEY— See "Grain" 

BEAN 

Anthracnose, Collet otrichum lindemuthianum (S. & M.) B. & C. — 
Spots on leaves, stems, and pods, up to two-fifths inch in diameter, 
dark-colored, usually with a red border and pinkish in the center. 
Very rare and unimportant in California. 

Mildew, Erysiphe polygoni D. C. — Forms a powdery white cover- 
ing over green parts of the plants; later brownish. May seriously 
reduce the vitality of the plants. Dust with sulfur at first appear- 
ance, or with sulfur nicodust if thrips or aphis are present. Some- 
times appears late where the pods are well formed. No treatment 
is necessary in that case. 

Rust, Uromyces appendiculatus (Pers.) Link. — Rust-colored spore 
masses or sori of pinhead size break through the lower surface of 
the leaf, with yellow spots above. Affected leaves are weakened and 
production decreases. Dust with sulfur at first sign of the disease 
and keep the surface of the soil dry by cultivation. Resistant varieties 
have been reported. 

Wilt or Stem Rot, Corticium vagum B. & C=Rhizoctonia, and 
Fusarium sp. — Many plants die while small from rot near the surface 
of the soil, while others wilt at different stages. Prepare the soil 
very thoroughly, plant as late as possible, avoiding cold and wet 
weather. Save seed from strong, well-matured plants. 



Circular 265] PLANT DISEASE AND PEST CONTROL 13 

Bean Aphis, Aphis rumicis Linn. — A small black louse collecting 
in great numbers on the leaves and tender tips. Use 5 per cent 
nicodust or spray with nicotine paste spray (Formula 27a). 

Bean Thrips, Heliothrips fasciatus Perg. — A small dark thrips 
with black and white wings. The larvae are white and pinkish 
and appear in great numbers on the lower surface of the leaves. 
Treatment the same as for bean aphis. 

Bean Weevil, Acanthoscelides obtectus Say. — The adults are short, 
robust, and about one-eighth inch long. The color varies from gray 
to brown with pale spots on the dorsum. The larvae work within 
the stored beans, from which the adults emerge through round holes. 
Breeding continues in storage. Fumigate in storage with carbon 
bisulfid, 10 to 30 pounds to every 1000 cubic feet of air space, the 
amount depending upon the tightness of the container. The temper- 
ature should be above 70° F. to secure satisfactory control by killing 
eggs, larvae, and adults. 

Garden Nematode. — See "General Subjects." Black eyes and 
Teparies are more resistant than other beans, but are sometimes 
badly infested. 

Red Spider or Two-Spotted Mite, Tetranychus telarius Linn. — A 
very small yellow, pale green or reddish mite, often with two large, 
or six small, dark spots on the body. Feeds on the under side of 
leaves and often spins a considerable web. If possible keep the 
beans well irrigated and cultivated and in good healthy condition. 
Begin sulfuring as soon as the mites appear and continue throughout 
the summer, using 90 parts of dry sulfur to 10 parts of finely ground 
dry hydrated lime. 

Wireworms. — See "General Subjects." 

BEET 

Curly-leaf =, Curly-top or Blight. — Transmitted by the beet leaf 
hopper, Eutettix tenella Baker. Leaf margins curl inward or rarely 
outward and are much dwarfed and deformed; plants are stunted 
and easily killed by drought and heat; young leaves show trans- 
parent venation (a clearing of the ultimate leaf vein branches), and a 
warty condition usually develops on the backs of veins on old leaves. 
Roots often become hairy and show dark rings in cross-section. In 
the cool districts subject to ocean fogs, the insects do not reproduce 
abundantly and the disease when established is less injurious. Beets 
in all other parts of the Pacific slope and of the Rocky Mountains 
are liable to injury, but in certain regions have been observed to 



14 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 

suffer less than in others. Early planting to bring the beet to 
a good size before the spring invasion of the insects from plains 
and foothills is generally successful except in years following early 
fall rains, which bring up filaree and other vegetation and cause a 
large number of insects to winter in the cultivated area. Blighted 
' ' stechlings ' ' do not produce seed successfully, although the symptoms 
may not always be apparent. 

The sugar beet leafhopper, Eutettix tenella Baker, referred to 
above is wingless in the immature form and winged when full grown. 
The adults average about one-fourth inch in length. The color varies 
with the season; those of the spring brood being pale green; those 
of the summer brood cream colored; while the winter generations 
are dark colored with darker markings on the wing covers. The 
insects are to be found chiefly on the under surfaces of the leaves or 
between the stems near the crown, thus producing the characteristic 
' ' curly-leaf ' ' described above. 

Downy Mildew, Peronospora schactii Fcl. — Inner leaves become 
curled, dwarfed, and covered below with a violet mildew. Develops 
in moist weather. Remove affected plants and destroy. 

Leaf Spot, Cercospora beticola Sacc. — Leaves have dead gray spots, 
mostly one-sixteenth inch in diameter or smaller with borders of 
brown or purple. Treatment not considered necessary. 

Rust, Uromyces betae (Pers.) Kuhn. — Powdery dark brown pus- 
tules of pinhead size appear on the green leaves. Not serious. 

Seedling Root Rot, Corticium vagum B. & C=Rhizoctonia, and 
Fusarium sp. — Roots are injured and become misshapen and forked; 
plants are delayed or stunted or die. Make the soil conditions as 
favorable as possible for vigorous growth. Replant if the stand is 
too thin. 

Armyworms and Cutworms. — See "General Subjects.' ' 

Beet or Spinach Leaf -miner. — See ' ' Spinach. ' ' 

Grasshoppers. — See ' ' General Subjects. ' ' 

Nematodes. — See "General Subjects." The beet is attacked by 
two species, the garden nematode, Heterodera radicicola Greef, which 
produces galls on a number of plants, and the beet nematode, H. 
schachtii Schmidt, which is confined to sugar beets and does not 
produce galls. 

Wireworms. — See "General Subjects," For the sugar beet wire- 
worm, Limonms calif ornicus (Mann.), plow in fall to destroy the 
pupae. Plant early and practice clean culture. Trap the adults 
by means of piles of straw and burn in late fall or winter. 



Circular 265] PLANT DISEASE AND PEST CONTROL 15 

BUSH FRUITS (Blackberry, Loganberry, Raspberry) 

Bluestem, Verticillium caulophagus (Law.) — Blackcaps and vari- 
ety Ranare are said to be particularly susceptible. Plants become 
sickly and canes die back; longitudinal dark streaks appear in the 
wood when the stems are cut across. Control not developed. Select 
plants from healthy fields. 

Cane Blight, Leptosphaeria coniothyrium Sacc, = Coniothyrium. 
— Dead areas appear on the canes, which are often girdled and killed. 
Cut out and burn all affected parts in the fall. Spray with Bor- 
deaux during the dormant season. Sometimes confused with anthrac- 
nose, which we have not recognized in California. 

If foliage and cane diseases are serious, there will probably be 
an advantage in removing the fruiting canes immediately after the 
crop is off, or at least before any moist autumn weather. Spray 
during the dormant season with lime sulfur 1-10 or Bordeaux 
(Formula 9, p. 74). Give proper irrigation and cultivation. If 
fields become unhealthy, reset in new land, using healthy plants. 

Crown Gall, Bacterium tumefaciens Sm. & T. — See "General Sub- 
jects." 

Fruit Mold, Botrytis and Other Fungi. — Avoid mixing bruised or 
moldy berries with good ones. 

Leaf Spot, Septoria rubi West. — Small dead spots on leaves and 
canes with brown or reddish borders. Liable to be severe on the 
variety mammoth and on wild dewberry. Treat as for cane blight 
above. 

Orange Rust, Gymnoconia interstitialis (Schlect.) Lagerh. — Indi- 
vidual plants are affected and ruined. New shoots come up pale, 
dwarfed and with the leaves curved inward and drawn upward. The 
surface of the leaves becomes covered with orange colored spores. 
Dig out and burn affected plants at the first appearance of the dis- 
ease. Spray healthy plants in the vicinity with Bordeaux mixture 
to prevent infection. 

Raspberry Horntail, Hartigia cressoni (Kirby). — The small white 
larvae are shaped somewhat like the letter ' ' S ' ' and when mature are 
nearly one inch long. They first attack the tender tips of the new 
canes and after girdling them and causing wilting they work down 
the pith to the roots, where they spend the winter. Cut off the young 
tips as soon as wilting is noticed so as to kill the larvae before they 
reach the roots. Remove all dead canes in winter, using care to dig 
out the borers at that time. 



16 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION 

Rose Scale, Aulacaspis rosae (Bouche). — A pure white scale 
often found in great numbers at the bases of the old canes. Spray in 
winter with distillate emulsion (Formula 23) or with miscible oil. 
Prune out old canes every year, because infestation spreads from them. 
Serious only where pruning is not practiced every year. Lime-sulfur 
used as a fungicide gives some control. 

The Blackberry Mite, Eriophyes gracilis (Nalepa). — This is a small 
microscopic mite causing the red-berry condition of the Himalaya 
blackberry throughout the state. The mites attack the drupelets of 
the berries shortly after the flowers open and continue to work in 
the fruit, preventing ripening. The winter is spent in the buds and 
the pest can be effectually controlled by spraying the infested vines 
in the early spring, in February or March, as the leaf buds are 
opening, with lime-sulfur solution, 4 gallons to 100 gallons of water. 

Summer control may be obtained by spraying with 5 pounds of 
wettable sulfur to 100 gallons of water. 

CABBAGE 

Yellows, Wilt, Fusarium conglutinans Woll. — Plants gradually 
turn yellow with falling of lower leaves. Stem shows dark ring when 
cut across. Loss may be severe. Reported as especially trouble- 
some on kale. Grow plants in soil free from disease. (See "soil 
disinfection," p. 95.) Avoid infected land. Certain strains of 
cabbage are resistant. 

Armyworm and Cutworms. — See "General Subjects." Scatter 
poison bran (Formula 4) broadcast over the ground and plants in the 
evening. 

Cabbage Aphis, Aphis brassicae Linn. — A small green aphis en- 
tirely covered with fine whitish powdery wax. Is best controlled by 
liberal and repeated applications of nicotine-distillate spray (Formula 
24) or of nicotine soap (Formula 27). Nicodust gives only partial 
control. 

Cabbage Worm, Pontia rapae (Linn.). — A small green, velvety 
worm, one inch long when mature, which feeds upon the leaves and 
destroys the heads. The adults are white butterflies with dark 
spots on the front wings. Young cabbage plants may be protected by 
using arsenate of lead, 1 pound of powder or 2 pounds of paste, to 
50 gallons of water. This should not be applied after the heads are 
formed because of possible poisoning of humans. Later control may 
be accomplished by applying a nicotine soap spray (Formula 27). 
A 5 per cent nicodust also gives very good control when liberally 
applied. 



Circular 265] PLANT DISEASE AND PEST CONTROL 17 

Cabbage Root Maggot, Phorbia brassicae Bouche. — The small white 
maggots, one-fourth inch long, are found tunneling the roots which 
are often completely destroyed by them. The insect also attacks 
radishes, turnips, cauliflower and other related plants. The most 
effective means of control is in the use of a repellent composed of 
1 ounce of corrosive sublimate to 10 gallons of water. Three appli- 
cations should be made, using one cupful (*/4 pint) around the base 
of each plant, as follows: 1st application 3 or 4 days after trans- 
planting ; 2nd application 9 or 10 days after transplanting ; 3rd 
application 19 to 20 days after transplanting. Later applications 
should not be made on account of the danger of poisoning the plants 
for market. The material may be applied with a watering can by 
regulating the flow. Clean up all refuse in the fall and plow and 
cultivate thoroughly during fall, winter and spring before trans- 
planting to expose and kill overwintering pupae in the soil. 

CAMELLIA 

Bud Blight. — Browning of the tips of the buds, followed by 
their decay and dropping, due frequently to injury from thrips. 
This should not be confused, however, with the dropping of the buds 
caused from lack of irrigation. 

CANTALOUPE. See ' ' Melon. ' ' 

CASABA. See "Melon." 



CELERY 

Blight, Cercospora apii Fr. and Septoria petroselini Desm. — Large 
or small dead spots appear on the leaves and leaf stalks, especially 
after cutting, and rapid deterioration follows. Spray repeatedly with 
Bordeaux (Formula 9), especially in moist weather, commencing in 
the seed bed. 

Aphids, Rhopalosiphum persicae (Sulz.) and Siphocoryne capreae 
(Fab.). — Green aphids attacking the stems and leaves of the plants. 
Spray with nicotine soap (Formula 27) or dust with 5 per cent nico- 
dust. 

Celery Caterpillar, Papilio zolicaon Boisd. — The caterpillars are 
beautifully marked, green, black and orange, and feed upon the leaves. 
Hand pick or spray with arsenate of lead not later than three weeks 
before harvest (Formula 2). 



18 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION 



CHERRY 

Armillaria, Wood Decay, Sour Sap. — See ''General Subjects." 
Gummosis, Die-back. — See "General Subjects." Several distinct 
troubles are involved, and frequently diagnosis is difficult. On cer- 
tain shallow soils it is reported that cherries die after a few years with 
copious gumming throughout the top. For bacterial gummosis it is 
recommended to grow Mazzard seedlings in the orchard and top work 
after several years with the desired varieties above the main forks. 
(See "Apricot.") Cherries are sensitive to excess of water in the 
soil and to summer drought and do not recover well from injury 
through soil defects. 

Leaf and Fruit Spot, Coryneum heijerinckii Oud. — See "Apricot," 
"Peach," "Almond." 

Leaf Curl, Exoascus cerasi Fuckel. — Leaves are affected in a way 
similar to peaches with peach leaf curl, but the symptoms less pro- 
nounced. (See "peach.") The treatment for peach leaf curl has 
been reported by practical orchardists to be successful on cherry. 
Rather rare. 

Leaf Spot, Coccomyces hiemalis = Cylindrosporium. — Tiny spots 
covering most of the leaf surface and becoming fused at the lower 
edge. Under side shows whitish coating of spores. Not serious as 
yet. Controlled in the East by Bordeaux mixture, 5-5-50, or lime- 
sulfur 1-50, adding iron sulfate 1% pounds, or dusting with sulfur. 
Applications as follows: (1) when the fruit is free from the calyx, 
(2) two weeks later, (3) just after the fruit is picked. 

Black Cherry Aphis, Myzus cerasi Fabr. — A shiny black aphid 
with long honey tubes, appearing in spring and early summer and 
causing severe curling of the leaves. Spray with nicotine and soap 
(Formula 27) or dust thoroughly with 5 per cent nicodust as soon 
as aphids appear. 

California Peach Borer. — See "Peach." 

Cankerworms. — See "General Subjects." 

Cherry Fruit Sawfly, Hoplocampa cookei (Clarke). — The small 
white larvae work within the partly developed fruits of the cherry 
and plum and are at times responsible for much damage. Their 
presence is indicated by the dropping of fruit and by the small round 
exit holes in fruits which are hardly half -grown. The best treatment 
is the application of arsenate of lead (Formula 2) just when the petals 
are opening. 



Circular 265] PLANT DISEASE AND PEST CONTROL 19 

Cherry Slug, Caliroa cerasi (Linn.). — The common name applies 
to the small dark green or blackish slug-like larvae which are nearly 
one-half -inch long and which feed upon the leaves in great numbers 
almost defoliating the trees in some years. Because of their slimy 
covering they are readily killed by the application of various dusts, 
such as finely ground hydrated lime, ashes, road dusts, etc., but are 
best controlled by the applications of 2 per cent or 5 per cent of nico- 
dust. The regular arsenate of lead sprays (Formula 2) are also good. 

Pear Thrips.— See "Pear." 

Red Humped Caterpillar. — See " Prune.' ' 

Tent Caterpillars. — See "General Subjects." 

CHRYSANTHEMUM 

Rust, Puccinia chrysanthemi Eoze. — Small dark pustules or sori 
appear on the lower side of leaves. Fertilize and irrigate freely to 
produce vigorous plants. 

Aphids (Various Species). — Spray with nicotine and soap (Form- 
ula 27) or dust with 5 per cent nicodust when the insects appear. 

Chrysanthemum Gall Fly, Diarthronomyia hypogaea (Low). — The 
small yellowish or white larvae cause numerous pointed galls on the 
leaves and stems and seriously injure the terminal buds. Great num- 
bers of minute slender red eggs are laid on the plants in the spring 
and early summer, and these may be readily killed by repeated appli- 
cations of nicotine and soap (Formula 27). Trim the plants to the 
ground in spring to eliminate hold-over forms. 

Chrysanthemum Leaf Miner, Phytomyza chrysanthemi Kow. — 
The injury due to this insect consists in numerous mines on the upper 
side of the leaves just under the epidermis. These are made by the 
small whitish maggots, which are easily killed within their burrows by 
applying one part of 40 per cent nicotine sulfate to 600 parts of water. 

CINERARIA 

Leaf Miner. — Injury similar to that of the chrysanthemum leaf 
miner and caused by the same insect. 

CITRUS FRUITS (Grapefruit, Lemon, Orange) 

Blast, Black Pit, Bacterium citriputeale C. 0. Smith. — Blast occurs 
only in very moist seasons and districts; black pit occurs with blast 
and also, rarely, in less moist localities. Blast is a watery deteriora- 
tion of leaves and petioles extending to a shield-shaped area in the 



20 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 

twig about the base of the leaf. Leaves die and dry up in place, the 
twig lesions turn dark, dry up, and heal, and shed off in two or three 
years. Where several leaves are killed, the twig may be much weak- 
ened or die. Black pit consists of dark, sunken spots in the rind 
of the fruit. They do not decay. Grow bushy, compact trees and 
avoid severe pruning. Protect the orchard with windbreaks against 
prevailing rain storms. For northern California conditions, spray 
from October to December with Bordeaux or ammonia copper car- 
bonate; repeat as soon as the fruit is off or before January 1 with 
Bordeaux. 

Blue Mold, Green Mold, Penicillium sps. — Rots the entire fruit, 
starting in spots and becoming a powdery blue or green, and gray. 
Avoid even minutest injuries in picking and handling fruit. 

Brown Rot of Lemon or Pythiacystis Rot, Pythiacystis citroph- 
thora, S. & S. — See also "Gummosis." This disease is distinct from 
brown rot of apricots or monilia rot. A rather light brown rot of 
fruit, causing only slight change in texture at first ; develops rapidly 
and spreads by contact. There is a characteristic odor and a slight 
surface mold in moist atmosphere. Develops in moist weather. When 
prevalent, spray the lower branches and ground beneath with Bor- 
deaux mixture (Formula 9). Straw mulch also is useful. Do not 
allow boxes of fruit to stand over night in the orchard. Use blue- 
stone in the wash water (Formula 12, p. 75), maintaining a constant 
strength of 1% lbs. to 1000 gals. Consult your farm advisor for 
special methods for keeping the strength of solution constant where 
alkaline water is used. Grade out very carefully all orchard infected 
fruits before storing. 

Cottony Rot, Sclerotinia libertiana Fcl. — See " Alfalfa," ''Apri- 
cot," etc. A serious citrus fruit rot in storage locally after wet 
weather. A snow white downy mold appears, causing a soft rot which 
spreads rapidly by contact. Twigs are sometimes killed. Treat- 
ment as for brown rot of lemon, but the spores are much more resist- 
ant. See the farm advisor or consult the University of California, 
College of Agriculture, for details in control. 

Damping Off, Armillaria Root Rot, Wood Decay. — See "General 
Subjects," p. 53. 

Gummosis, Phythiacistis citrophthora Smith & Smith. — Copious 
exudation of gum on the lower part of the trunk. The bark of the 
affected part dies and the diseased area may continue to spread until 
the tree is girdled and killed. Cut out all affected bark as soon as dis- 
covered and treat the wounds with Bordeaux paste (Formula 10, 



Circular 265] PLANT DISEASE AND PEST CONTROL 21 

p. 74). Do not allow water to stand about the base of trees. In 
planting keep the point of budding well above ground and never allow 
the soil to pile up around the trunk. For heavy soil, use trees high- 
budded on sour orange root. See also " General Subjects," p. 56. 

June Drop. — Young fruits up to nearly 1 inch in diameter turn 
pale and drop off. Especially troublesome with navel oranges during 
severe hot periods. Any deficiency in vigor of the tree or of moisture 
supply in the soil will presumably make the trouble worse. Build up 
the vigor of the trees; secure the best possible moisture condition of 
the soil ; plant windbreaks. Consult your farm advisor or local 
authorities. 

Mottled Leaf. — Add as much organic matter to the soil as possible 
in the form of green manure crops, bean straw, and manure. Avoid 
continual fertilization with nitrate of soda. See that water pene- 
trates to the subsoil and keeps it uniformly moist. See "General 
Subjects," p. 57. 

Scaly Bark. — Bark at first becomes roughened in a small area; 
roughening spreads and deepens, finally gumming heavily, encircling 
the trunk or limb and causing its death. Scrape off all visibly affected 
bark, leaving the inner bark, extending 2 or 3 inches beyond the 
edges of the spot. Cover the wounds with Bordeaux paste (Formula 
10) or other suitable fungicide. Cut off badly affected branches. 
Watch all trees very closely in groves where the disease is present 
and eradicate new cases at first appearance. Do not use Bordeaux 
if the trees are soon to be fumigated. 

Aphids (Various Species). — Use nicotine and soap spray (Formula 
27 or a 5 per cent nicodust. 

Armyworms and Cutworms. — See "General Subjects." 

The European Red Mite, Paratetranychus pilosus C. & F. and the 
Two-Spotted Mite, Tetranychus bimaculatus Harvey. — The first is 
bright cardinal red, while the two-spotted mite is yellow, pale green 
or reddish and often has two or six dark spots on the dorsum. Dust 
with sulfur or spray with lime-sulfur 1-50 or wettable sulfur (Form- 
ula 14), or commercial sulfur paste 10 pounds to 100 gallons of water. 

Citrus Thrips, Scirtothrips citri (Moult.). — Small pale yellow in- 
sects less than one-thirtieth inch long working in blossoms and on 
leaves and fruit. This insect is most satisfactorily controlled by a 
2 per cent solution of commercial lime-sulfur, but may also be con- 
trolled by using the Government formula for pear thrips (Formula 
24) or by applications of 6 per cent nicodust. A combination of mis- 



22 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 

cible oil and lime-sulfur is recommended by some for killing the gray 
citrus scale (Coccus citricola Campb.) and the citrus thrips at the 
same time. 

Fuller's Rose Beetle, Pantomorus fulleri (Horn.). — A small 
gray snout beetle three-eighths inch long which attacks young buds 
and foliage of citrus trees. The adults cannot fly and may be kept 
off the trees by cotton or tanglefoot bands around the trunks. 

Mealybugs (Various Species of Pseudo coccus). — These small, flat, 
oval insects, covered with white mealy material, are well known to most 
citrus growers. They are difficult to control, but may be most satis- 
factorily handled by liberal applications of carbolic acid emulsions 
(Formulas 26 and 26a) and by miscible oils. Washing with water 
under heavy pressure has proved satisfactory under certain conditions. 
For the citrus mealy bug, parasites are used with splendid results 
along the coast. The control of ants is necessary to secure beneficial 
results from natural enemies. See "Ants. " 

Scale Insects (Many Species). — Fumigation with hydrocyanic acid 
gas is best, although some orchardists secure good results, particularly 
for soft brown and gray citrus scales, by repeated and thorough appli- 
cations of various strengths of distillate emulsions (Formulas 20 and 
23) and miscible oils. 

CORN 

Boil Smut or Common Smut, Vstilago zeae (Beckm.) Ung. — Tender 
tissues of tassel, ear, or stalk swell into large soft masses, which dry 
out, becoming fragile and filled with black dust. Somtimes gather- 
ing up and destroying the smutted stalks before the smut balls dry 
is recommended. Seed treatment is not effective. Often serious in 
California. Rotation is perhaps useful. Diseased corn trash and 
manure are infectious. 

Ear Mold, Diplodia zeae (Schw.) Lev. and Fusarium sp. — The ears 
mold in the field, the kernels becoming crusted together and light. 
Sometimes bad in late corn in shallow soil. Use early varieties. Har- 
vest and cure as early as possible. Avoid over-irrigation. 

Head Smut, Sphacelotheca reiliana (Kuchn.) Clint. — Ear and 

whole top of plant are affected. No grain formed. See ' ' Sorghum. ' ' 

Angoumoise Grain Moth. — See "Grain." 

Armyworms and Cutworms.— See "General Subjects." 

Corn Earworm, Chloridea obsoleta (Fab.). — The larvae are nearly 

two inches long when full grown and vary in color from yellowish to 

brownish, with longitudinal gray and white stripes and with eight 



Circular 265] PLANT DISEASE AND PEST CONTROL 23 

small dark tubercles on each segment. They work chiefly on the corn 
in the ear, but may also attack the tassels and leaves. Clean up and 
burn refuse in the field. Plow in fall or early spring to expose and 
kill the pupae. Repeated dusting of ears with powdered arsenate of 
lead one part to four parts of hydrated lime gives some relief. 

Granary and Rice Weevils. — See ' ' Grain. ' ' 

Grasshoppers. — See "General Subjects." 

Wireworms. — See "General Subjects." 

COTTON 

Bean Thrips. — See "Bean." This insect usually appears on the 
cotton late in the season, when the injury is not of sufficient importance 
to justify control. Early infestation should be promptly dealt with. 

Corn Earworm. — See "Corn." Attacks the cotton bolls. Sweet 
corn is sometimes planted as a catch crop. Dusting with powdered 
arsenate of lead or calcium arsenate gives good results. 

Cotton Leaf Perforator, Buccidatrix thurberiella Busck. — The 
larvae are pale or dark greenish and less than one-half inch long. 
When disturbed they wriggle violently. The work consists in per- 
forating the leaves with very many holes so as to almost entirely 
consume them. The larvae pupate in small, white-ribbed cocoons 
attached to the leaves or stems of the plants. The adults are white 
with black dots and other black markings. 

This insect normally feeds upon wild cotton, but in recent years 
has invaded the cotton belt of the Southwest, and, while it prefers weak 
plants, it will attack perfectly healthy ones as well. 

Parasites do much to keep the insect in check but where severe 
infestations occur dust plants with calcium arsenate alone or with lead 
arsenate, one part to four parts of hydrated lime. From 20 to 30 
pounds are sufficient for an acre of cotton. 

Red Spider or Two-Spotted Mite, Tetranychus telarias Linn. — See 
"Bean." 

CUCUMBER 

Mildew, Erysiphe cichorearum D. C. = Oidium. — Fine white my- 
celium covers the leaves. Dust with sulfur at first appearance or with 
sulfur nicodust if the melon aphis is also present. 

Flea Beetles (Various Species). — Small flea-like beetles which 
jump quickly and eat small holes in the leaves. Bordeaux mixture 
(Formula 9) as a repellent is the best control measure. This treat- 
ment is also recommended for mildew. 



24 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 

Garden Nematode. — See ''General Subjects." 

Melon Aphis.— See "Melon." 

Red Spider or Two-Spotted Mite.— See "Bean." 

Western Twelve-Spotted and Striped Cucumber Beetles, Diabe- 
tica soror Lee. and D. trivittata Mann. — The former is a small green 
beetle with twelve black spots on the back and is often mistaken for a 
ladybird; the latter is a brown beetle with three black lines on the 
dorsum. The white larvae feed upon the roots and may be controlled 
by pouring on the roots a cup of 40 per cent nicotine sulfate diluted 
1 to 1000 parts of water. Bordeaux mixture (Formula 9) is of con- 
siderable value as a repellent. Arsenate of lead (Formula 2) may also 
be used with good effect. 

CURRANT, GOOSEBERRY 

Mildew, Sphaerotheca mors-uvae (Schw.) B. & C. — A fine white 
mycelium grows over the young leaves and shoots and checks their 
development. Serious on some varieties. The best treatment is to 
spray with lime-sulfur 1-33 when buds commence to open and two or 
three times thereafter at intervals of 10 to 14 days. Where serious 
cut and burn diseased tips of canes while dormant, as the fungus win- 
ters in them (from U. S. D. A. Farmers' Bull. 1024). In California, 
where resistant varieties are used, a dormant spray of lime-sulfur 1-10, 
followed by dusting with sulfur when the disease first appears, has 
generally been effective. 

Currant or Gooseberry Fruit Fly, Epochra canadensis Loew. — 
Small white maggots in the fruit at picking time. Cultivate thoroughly 
during the fall, winter, and spring months to expose and destroy the 
hibernating pupae. 

Flat-Headed Apple Tree Borer.— See "Apple." 

Imported Currant Borer, Aegeria tipuliformis Clerck. — White 
caterpillars nearly one inch long working down the middle of the stalks 
and into the roots of the plants. Cut out and burn all dead and in- 
fested canes during winter and remove the borers. 

Red Spider or Two-Spotted Mite, Tetranychus telarius Linn. — See 
"Bean." Dust with sulfur or spray with wettable sulfur (Formula 
14) or sulfur paste (Formula 13.) 

San Jose Scale. — See "Apple." 

Combined Spraying 
The sulfur sprays will control both the mildew and the red spider. 



Circular 265] PLANT DISEASE AND PEST CONTROL 25 

DAHLIA 

Mildew, Erysiphe sp. — White spots spread over lower leaves. Not 
serious. Dust with sulfur. 
Bean Aphis. — See "Bean." 
Western Twelve-Spotted Cucumber Beetle. — See "Cucumber." 

DATE 

Date Palm Scale, Parlatoria blanchardi (Targ.). — A small gray 
and white scale, less than one-sixteenth inch long, often occurring in 
great numbers on the leaves. It may be controlled by cutting away 
and destroying all the leaves, burning over the trunk with a gasoline 
torch. Offshoots are cleaned up by heavy fumigations with hydro- 
cyanic acid gas. This insect is quarantined by the Federal Horticul- 
tural Board, and young plants may be obtained only from uninfested 
territory. 

Dried Fruit Beetle.— See "Prune." 

Indian Meal Moth. — See "Prune." This insect is a serious pest 
to dried dates, of which small amounts are preferably put up only in 
insect-proof containers to prevent infestation. 

Marlatt Scale, Phoenico coccus marlatti Ckll. — A red-bodied, cot- 
tony covered scale, considerably larger than the date palm scale. It 
is chiefly found in the unfolding leaves, often so protected as to be 
almost impossible of control. Fumigating and burning over the 
trunks and treating liberally with carbolic acid and oil emulsions give 
some control, but eradication on a tree once thoroughly infested is 
apparently impossible. This pest is also under federal quarantine, 
and new plants may be obtained only from uninfested territory. 

Red Spider.— See "Citrus." 

FERNS 

Black Scale and Plant Lice. — Dip the plant frequently in a solu- 
tion of 40 per cent nicotine sulfate, 1 part to 600 parts of water. 

FIG 

Dropping of Fruit. — Usually due to lack of caprification by the 
minute fig wasp bringing pollen to the flowers from the wild or 
Capri fig. Applies only to certain varieties as the Calimyrna. Con- 
sult literature on fig culture and authorities on the subject. 



26 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION 

Smut, Aspergillus niger V. Tiegh. = Sterigmatocystis ficuum 
(Reich.) Henn. — Caused by one of our commonest molds. Infection 
occurs in ripening fruit ; if at an early stage, the fruit rots, if later it 
is harvested. In extreme cases the dried fruit is merely a shell filled 
with purplish black dry powder which may be puffed out. There 
are all gradations to the condition in which the interior of the fig 
is merely slightly darkened. Affected fruit is said not to give an 
offensive flavor, nor to be injurious to health. Does not develop in the 
stored dry figs. Remedies not yet developed. 

Souring and Splitting. — Due to unfavorable atmospheric and soil 
moisture conditions. Choose suitable localities and regulate the soil 
moisture with greatest care. 

At least two canker diseases are known in California, and twig 
blight is caused to a limited extent by Sclerotinia libertiana and 
Botrytis cincrea. Frost is often injurious to young trees which make 
late growth. (See "General Subjects.") None of these appears to 
be serious. 

Branch and Twig Borer. — See ' ' Apricot. ' ' 

Mediterranean Fig Scale, Lepidosaphes ficus (Sign.). — Scales re- 
semble small oysters and infest the limbs, twigs, leaves, and fruit. 
Spray with distillate emulsion (Formula 23), miscible oil or crude 
oil emulsion (Formula 18) during the winter when the trees are 
dormant. 

Nematodes. — Becoming increasingly serious. No remedy known. 
See "General Subjects." 

Pomace or Vinegar Fly, Drosophila melanogaster Meigen. — Small, 
slender, whitish maggots and brown or orange-colored flies one-tenth 
inch long, often occurring in great numbers in figs on the trees and 
on the drying trays. 

GRAIN (Barley, Oats, Wheat) 

Rust, Puccinia sps. — Pustules of pinhead size, round or elongated, 
break through the surface of leaves and stems ; mostly reddish at first 
and dusty ; later black. Serious in heavy grain in moist situations or 
seasons. No remedy known but resistant varieties may be used. 

Smut, Ustilago sps. and Tilletia sps. — Mature grain has black con- 
tent and gives off characteristic odor. Seed of wheat, barley, oats, 
Sudan, millet, and sorghum should be carefully cleaned of smut balls, 
weed seeds, and small, cracked, and inferior grains before treating. 
The smut balls in wheat and smut masses in barley may be cleaned out 



Circular 265] PLANT DISEASE AND PEST CONTROL 27 

in fanning mills or floated out in water and skimmed off. Place the 
cleaned seed in half-filled sacks tied at the end. Immerse these sacks 
for three or four minutes in a bluestone solution made by dissolving 1 
pound of bluestone in 5 gallons of water (Formula 11). Drain the 
sacks until dripping no longer occurs, then dip them for three minutes 
in a milk of lime made by slaking 1 pound of quicklime in 10 gallons of 
water. The lime prevents injury to the germ from bluestone. If 
quick-lime cannot be secured, air-slaked lime, 1 pound to 8 gallons of 
water may be used. After this treatment the grain should be spread 
out to dry, after which it may be planted or stored. 

Oats are especially sensitive to bluestone, and for them it is better 
to use a solution of formaldehyde, 1 pound to 40 gallons of water, for 
ten minutes. After this no lime dip is needed. Barley is more sensi- 
tive than wheat and should always be lime-dipped after treatment with 
bluestone. 

Seed scratched or injured in threshing should be limed after dip- 
ping in bluestone solutions. Scoured seeds should not be dipped in 
any fungicidal solution. 

Seed wheat and barley to be sown in dry ground or to be stored 
longer than 48 hours must not be treated with formaldehyde, as severe 
injury may follow. 

If foggy or rainy weather is liable to interfere with the proper 
drying of lime-treated seed, heating injury may be avoided by soaking 
the seed for 10 or 15 minutes in water before dipping in the bluestone 
solution. The lime dip may then be omitted. 

Copper carbonate dust has been highly successful in controlling 
bunt, but is not so successful with other smuts. The copper carbonate 
dust does not cause seed injury, and appears to stimulate growth. 
Dusted seed may be stored dry for long periods without injury to 
seed. A number of serviceable machines for applying the dust are on 
the market. Finely powdered bluestone also gives good smut control, 
but is not equal to copper carbonate, for seed injury may occur in 
badly scratched or broken seed. 

Loose smuts of wheat and sorghum cannot be controlled by the 
above treatment. Loose smuts of oats and barley are destroyed by 
formaldehyde solution (1 pint to 30 gallons of water), soaking for 10 
minutes. Kernel smut of sorghums and Sudan grass is controlled by 
soaking the seed in formaldehyde solution, as above, for 30 minutes for 
grain sorghums and 60 to 90 minutes for sweet sorghums and Sudan. 
Ergot of rye and rye grass is controlled by floating off the ergots in a 
strong brine solution (40 pounds salt in 25 gallons water) and rinsing 
with clear water, or by holding the seed for a year before sowing. 



28 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION 

Angoumoise Grain Moth, Sitotroga cerealla Oliv. — A small tawny 
moth found in granaries. The pale yellow caterpillars feed within 
the kernels of stored grain and corn, escaping through a round hole. 
Control measures are the same as for the granary and rice weevils. 
See below. 

Aphids (Many Species). — Aphids often seriously attack grain. 
Control methods are usually too costly to be practicable. Cutting is 
often resorted to in order to save that part of the crop. 

Armyworms and Cutworms. — See "General Subjects." 

Grain Mites, Tyroglyphus sps. — Pale-colored mites, smaller than 
the head of a pin. Frequently found in grain and by-products. 
When abundant, they appear as loose, fluffy masses of gray powder 
as the cast skins are mingled with the living mites. Heat is the most 
effective remedy and should be used if practical. (See "Heat," 
p. 94.) Fumigation with carbon disulfid may also be used. Screen- 
ing or fanning may reduce the infestation to a satisfactory degree. 

Granary Weevil, Calandra granaria Linn., and Rice Weevil, C. 
oryzae Linn. — Small brown weevils not over one-sixth inch in length, 
attacking the grain in storage. Fumigate with carbon disulfid, 10 
to 30 pounds to 1000 cubic feet of air space, according to the tightness 
of the container. The temperature must be at least 70° F. for satis- 
factory results. Hydrocyanic acid gas may also be used as a f umigant, 
in which case from 1 to 4 ounces of pure sodium cyanid to 100 cubic 
feet of air space should be used. Heating the grain to 125° F. for 
several hours will kill all the weevils. Keeping the grain dry and well 
ventilated will largely prevent weevil attack in storage. 

Grasshoppers. — See ' ' General Subjects. ' ' 

GRAPE, RAISIN 

Coulure. — In certain varieties notably Muscat, the flowers some- 
times fail to set fruit. Interplanting with other varieties to im- 
prove pollination is recommended. Also vigorous sulfuring during 
blossoming to prevent mildew favors the setting of fruit. 

Crown Gall = Black Knot, Bacterium tumefaciens S. and T. — 
Rough galls form on canes and trunks above ground; often serious. 
Girdled stems become weakened and die. Bad in cold situations and 
following frosty seasons. If spoiled parts are removed in time, 
new shoots will grow up from below. Control not worked out, but 
something can be done by surgery. Bordeaux spray in winter should 
be tried as preventive. See "General Subjects," p. 55. 



Circular 265] PLANT DISEASE AND PEST CONTROL 29 

Little Leaf , Apoplexy, Black Measles, Obscure Diseases. — See 
''Physiological Diseases," p. 57, under "General Subjects." 

Mildew, Uncinula spiralis B. & C. = l\ necator <Schw.) Burr. — 
White mycelium spreads over young leaves, canes and fruits, checking 
growth ; the leaves are deformed and may drop ; the surface of the 
fruit hardens and darkens and the fruit often cracks, or may drop. 
Dust vrith sulfur when the shoots are about 6 inches long and again 
just before the -blossoms open, being careful not to miss a single leaf. 
If the vines were affected the previous year do not wait until the 
mildew appears. In cool or moist locations a third sulfuring when 
the grapes are as large as peas and a fourth when they are two-thirds 
grown may be necessary. In these later treatments the sulfur should 
be dusted only on the fruit and the centers of the vines. If the larvae 
of leaf -hoppers are present use nico-sulfur instead of sulfur. 

Achemon Sphinx Moth, Pholus achemon (Drury). — Large green 
and pinkish caterpillars with oblique whitish bars on the sides. Often 
abundant and doing great damage by stripping the vines. ' Adult 
moths dull gray with brown marks and pink hind wings. Spray vines 
with arsenate of lead (Formula 2), to which is added 1 pint of 40 
per cent nicotine sulfate to every 200 gallons, or dust with powdered 
arsenate of lead. 1 part to 4 parts of hydrated lime or flowers of sulfur. 

Armyworms and Cutworms. — See "General Subjects." 

California Grape Root Worm, Bromius ooscurus (Linn.) — The 
adult beetles are black or brown and three-sixteenths inch long. They 
eat long slender holes in the leaves. The small white grubs feed on 
the roots of the vines. Cultivate thoroughly close to the vines during 
the winter to kill hibernating larvae. As soon as the beetles appear in 
the spring spray with arsenate of lead, 6 pounds of paste or 3 pounds 
of powder to 100 gallons of water, or dust with 1 part of powdered 
arsenate of lead to 4 parts of hydrated lime or sulfur. 

Dried Fruit Beetle. — On raisins, see "Prune." 

Grape Leaf-hopper, Erythroneura comes (Say). — The immature 
forms or nymphs are white or pale yellow, while the adults are pale 
yellow with numerous small reddish marks all over the dorsum. All 
forms feed on- the under side of the leaves, causing them to turn yellow 
and drop prematurely. Clear weeds and refuse from around the 
vineyards and practice clean culture to reduce the number of over- 
wintering adults. Before the young nymphs develop wings spray 
thoroughly with nicotine and soap (Formula 27). or with the follow- 
ing:: 40 per cent nicotine sulfate, 1 pound; liquid soap, 1 3 gallon (hard 



30 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION 

soap, 2 pounds) ; water, 200 gallons. The young and adults may also 
be killed by thoroughly dusting with a 10 per cent nicodust, or a 
6 per cent nicosulfur dust, which latter will also control mildew. 

Grape Phylloxera, Peritymbia vitifoliae (Fitch). — The presence 
of the phylloxera is indicated by weak and dying vines. It usually 
occurs in spots. The insect is a minute, yellow louse which feeds on 
the roots. To disinfect cuttings or rootings before planting, dip in 
hot water 122° F. for five minutes. For permanently resistant vines, 
graft European varieties on certain American roots. (See Circular 
No. 226, Calif. Agr. Exp. Sta., Univ. of Calif., Dec, 1920.) 

Grasshoppers. — See "General Subjects." 

Indian Meal Moth. — On raisins, see "Prune." 

Mealybug, Pseudococcus maritimus Ehr. = P. bakeri Essig. — 
Easily distinguished by the small oval, flat bodies covered with white 
cotton-like wax and by the cottony egg masses among the bunches of 
grapes. , Difficult of control, but best results have been obtained by 
burning sulfur under a tent over the vines. (See Monthly Bull., Cal. 
State Dept. Agr., Sacramento, Vol. IX, p. 26, 1920). Also see "Pear." 

HOLLYHOCK 

Rust, Puccinia malvacearum Mont. — Prominent red sori or pus- 
tules push out on the lower surface of the leaves and on petioles and 
stems, often causing distortion. Fertilize and water freely to promote 
vigorous growth. 

Destroy all old plants and start anew from seed at least every 
two years. Some strains appear to be resistant. 

The Painted Lady Butterfly, Vanessa caryae Hubn. — The yellowish 
or black spiny caterpillars, which are about one inch long, feed on 
the leaves, which they draw together with webs for protection. Con- 
trol is best accomplished by using 40 per cent nicotine sulfate, 1 part 
to 600 parts of water, and spraying the plants thoroughly. 

HOP 

Hop Aphis, Phorodon humuli (Schr.). — A pale green aphid at- 
tacking the young shoots and leaves. Dust thoroughly and as often 
as necessary with 5 per cent nicodust or spray until injury ceases with 
nicotine and soap (Formula 27.) 

Hop Flea Beetle, Psylliodes punctulata Mels. — A small green or 
bronze metallic beetle, one-tenth inch long, attacking the foliage. 



Circular 265] PLANT DISEASE AND PEST CONTROL 31 

Jumps quickly when disturbed. The most efficient method of control 
consists in putting tanglefoot bands around the bases of the vines and 
around the poles. These not only prevent the beetles from climbing 
the vines but catch great numbers of them. 

Red Spider or Two-Spotted Mite.— See "Bean." 



LAWNS 

Earth Worms. — Earth worms or angle worms frequently cover 
golf greens with casts of earth, which are undesirable in such a 
place. To cause the worms to come to the surface, apply corrosive 
sublimate, mixed as follows, and then sweep up the worms and remove 
them : — 

1 lb. corrosive sublimate. 

1 gallon boiling water. 

Let cool for one hour; then add 4 gallons of cold water. Use 
2% pints of this solution to a barrel of water, and apply to greens 
with a sprinkler. See p. 90 for precautions in the use of corrosive 
sublimate. This is a dangerous poison. 

Weeds. — Fertilize well. Use a solution of nitrate of soda, strong 
enough to kill the tops but not the roots — about 3 to 5 pounds to 
100 gallons af water, depending on the kind of grasses in the lawn. 

Wireworms. — Lime water applied to the brown places in the lawn 
will drive out wireworms. 

LOQUAT 

Pear Blight, Bacillus amylovorus (Burr.) Detoni. — Limb and body 
blight is sometimes very severe. See "Pear." 

Scab, Fusicladium eryohotryae Sciala. — Resembles scab of pear 
and apple, but is more injurious to expanding foliage. (See ' ' Pear. ") 
Control is not developed but sprays for pear in foliage may probably 
be used. 

Green Apple Aphis. — See "Apple." 

San Jose Scale. — See "Apple." 

MELON (Casaba, Cantaloupe, Pumpkin, Squash, Watermelon). 

Blossom End Rot. — Is presumably associated with soil or climatic 
conditions. Sometimes severe. There is indication of resistance in 
some varieties. 



32 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION 

Wilt, Fusarium sp. — Well-grown watermelon plants wilt and die, 
leaving the field nearly bare. Plant on fresh soil. Watermelons can- 
not be grown for several years on infected ground. Other melons are 
not often, if ever, affected in California. 

Flea Beetles. — See ' ' Cucumber. ' ' 

Melon Aphis, Aphis gossypii Glover. — A small, dark green louse 
occurring in great numbers on the plants and doing great damage. 
Destroy first infested plants as soon as discovered in spring or spray 
with nicotine sulfate, 40 per cent, 1 part to 1000 parts of water. A 
5 per cent nicodust also gives very good results and is much more 
easily and quickly applied. 

Nematode. — See * ' General Subjects. ' ' 

Squash Bug, Anasa tristis De Geer. — The young bugs are gray 
with black antennae, legs, and thorax; the adults of a uniform dull 
grayish-brown above, mottled yellowish beneath, and about three- 
quarters inch long. Control measures should be directed against the 
immature forms, and consist in the use of 1 part of 40 per cent 
nicotine sulfate to 600 parts of water. A 10 per cent nicodust kills 
many. Hand picking the adults in the spring is successful in small 
gardens. 

Western Twelve-Spotted and Striped Cucumber Beetles. — See 
"Cucumber." 

NURSERY STOCK 

Failure to Grow After Planting in Orchard. — Very rarely due to 
specific disease. Usually caused by freezing, drying, or water soaking 
of trees before or after planting ; planting too deep ; cold, wet, or hot 
weather after planting ; or some other condition unfavorable to growth. 
Bare roots are very sensitive to slight freezing and injured trees 
at best start tardily and grow in a sickly way. Buy from the 
nearest reputable nursery. Pay for good trees and see that they 
are handled and planted carefully. Replant all that do not grow 
well the first season. 

Citrus Trees. — For scale insects, defoliate and fumigate with 
hydrocyanic acid gas. (See p. 89.) Rejecting infested stock is the 
only safe procedure. 

Deciduous Trees. — For borers and other insects, fumigate with 
hydrocyanic acid gas. Rejecting infested stock is the only safe 
procedure. 

Nematode, Crown Gall. — Very carefully avoid planting affected 
trees. If a large percentage of a plot of trees is affected, those appar- 
ently healthy are of doubtful value. See ''General Subjects. 7 7 



Circular 265] PLANT DISEASE AND PEST CONTROL 33 

Pythiacystis Canker or Brown Rot of Lemon, Pythiacistis citroph- 
thora S. & S. — Dead spots up to several inches long develop on the 
trunk or branches, mostly above the bud union. Caused by soil 
infection under very wet conditions. Spray trees with Bordeaux 
mixture before digging and after healing in. Soil for healing in 
should be well drained or under cover. Active only in very wet 
seasons. 

OAT. See Grain 

OLIVE 

Armillaria, Wood Decay. — See under ''General Subjects," p. 53. 

Die-back = Exanthema. — Bushy phase characterized by repeated 
death of terminal buds and branching out below ; leaves show deform- 
ities. In die-back phase there is usually dropsy-like puffing of bark 
on branches and limbs and unusual prominence of lenticels in the 
smooth bark, with dying back. Secure uniform moisture and good 
drainage. Add organic material to soil by green manure crops, mulch, 
or manure. Replace olives with plums, peaches, or other crop where 
die-back is very bad. See "Physiological Diseases," under "General 
Subjects. ' ' 

Dry Rot, Bitter Pit. — Dry spots appear in the flesh of the fruit. 
(See "Physiological Diseases," under "General Subjects.") No 
effective treatment known except good general care. 

Olive Knot =. Tuberculosis, Bacterium savastanoi E. F. Smith = 
Pseudomonas oleae. — Rounded, rough swellings, from very small up 
to several inches in diameter, appear on twigs, limbs, trunk, or roots, 
mostly at leaf scars or wounds, also rarely on fruit pedicels and leaves. 
Cut out thoroughly at first appearance and disinfect. (See "Pear 
Blight" and "Crown Gall.") The Mission is more resistant than the 
Manzanillo or some oil varieties. 

Peacock Spot, Cycloconium oleaginum Cast. — Blackish round 
spots, one-eighth to one-quarter inch in diameter, on the surface of 
green leaves but not killing the darkened area. Is apparently of 
very slight importance in California. 

Black Scale, Saissetia oleae (Bern.). — See "Apricot." Attacking 
chiefly the twigs. Spray with distillate emulsion (Formula 23) or 
miscible oil, December to February. 

Branch and Twig Borer, Poly coon confertus Lee. — See ' ' Apricot. ' ' 
This is often a serious pest of young olive trees. 



34 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 

Ivy or Oleander Scale, Aspidiohcs hederae Vail. — A small circular, 
flat, gray scale occurring on the leaves and fruit, somtimes causing 
discolored spots on the ripening olives. Control as for black scale. 

Olive Bark Beetle, Leperisinus californicus Swaine. — The small 
white larvae work in the cambium layer just under the bark and the 
adults bore small, round exit and entrance holes through the bark. 
Occurs in the southern part of the state. Burn prunings and remove 
all dead and infested portions of the trees. 

ONION 

Downy Mildew, Peronospora schleideni Ung. — Areas on leaves or 
stems show a violet-tinted fuzz. These areas rapidly fade and collapse 
if the weather is moist, and the disease may spread rapidly. Not suc- 
cessfully controlled in wet seasons. Bordeaux mixture found useful 
in some cases; it should be used with resin fish-oil soap or other 
spreader. See ' ' Spreaders, ' ' pp. 68-69 ; also ' ' Asparagus. ' ' 

Pink Root, Fusariam malli Taub. — Young plants are stunted and 
older plants are injured, bulb formation is interfered with and the 
crop reduced. Roots diseased turn pink. Avoid infected soil, or 
if not entirely possible keep plants growing as well as possible at 
all times. Where plants are grown in a seedbed and transplanted, 
use healthy soil, or disinfect with formaldehyde or steam, p. 95. 

Scullions. — Plants fail to form bulbs, the stalks remaining thick 
and green. May be due to poor seed or to a check in growth. Plant 
at a suitable season so that development may be continuous. Cutting 
off seed stalks and breaking over tops when crop is maturing may 
help. 

Armyworms and Cutworms. — See "General Subjects." 

Onion Maggot, Hylemyia antiqua Meig. — Small, white maggots 
attacking the onions beneath the ground. Practice clean culture and 
destroy all refuse onions in the fall. Plow and cultivate thoroughly 
during winter and spring. Considerable protection is gained by 
spraying the plants repeatedly with carbolic acid emulsion. (Form- 
ula 26, diluting stock solution 1 to 40.) 

Onion Thrips, Thrips tabaci Lind. — Minute, slender, pale yellow 
insects occurring in great numbers on the leaves, causing them to turn 
gray and wither. Spray with 1 part of 40 per cent nicotine sulfate 
to 800 parts of water or apply 5 per cent nicodust. 

Wireworms. — See "General Subjects." 



* 



Circular 265] PLANT DISEASE AND PEST CONTROL 35 



PEA 

Bacterial Blight or Bacteriosis, Pseudomonas pisi Sack. — Exten- 
sive, watery, olive green blisters appear on stems and leaf bases in 
wet weather, following cold. Some affected areas dry up, others kill 
the stem. Where the injury does not go too far down, new stems 
grow from below. In some wet situations practically every plant 
has been killed. Control not developed, but the trouble is worse in 
cold wet situations. 

Blight or Spot, Mycosphaerella pinodes Berk. & B\ox.=Ascochyta. 
— Sunken dead spots form on pods, leaves, and stems, one-quarter 
inch or less in diameter; center of spot on pod becomes gray or 
pinkish, with a dark border; on leaf and stem spots are more often 
merely dark. Young stems may be killed. Experiments indicate 
spraying is impractical. Keep pea crop and diseased material off 
the land for two years. Seed infection rare in California. Avoid 
too low, wet land. 

Downy Mildew, Peronospora trifoliorum De Bary. — Resembles 
downy mildew of Alfalfa. (See p. 1.) Common at the close of the 
rainy season, but apparently not serious. 

Mildew or Powdery Mildew, Erysiphe polygoni D. C. — Powdery 
white growth spreads over the foliage, injuring plants. Troublesome 
in summer or when rains are light or lacking. Dust with sulfur on 
first appearance or nicosulfur dust if aphids are abundant, and 
repeat if necessary. 

Armyworms and Cutworms. See "General Subjects." 

Pea Aphis, Macrosiphum pisi (Kalt.). — A large green aphid at- 
tacking the terminal shoots and leaves of the vines. It is difficult of 
control because of the expense involved, but may be killed by repeated 
applications of a 10 per cent nicodust or a nicotine spray (Formula 
27a) or a 6 per cent nicosulfur dust to also control mildew. 

Pea Weevil, Bruchus pisorum Linn. — A small gray and white 
weevil attacking the pea, much as the bean weevil attacks the bean, 
but the pea weevil infests the peas in the field and the adults do not 
emerge until the following spring. Unlike the bean weevil, however, 
it never reinfests stored peas. Treatment is the same as for bean 
weevil. See "Bean." 



36 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 



PEACH 

Armillaria, Wood Decay, Crown Gall, Nematode. — See "General 
Subjects," p. 53. 

Brown Rot, Sclerotinia cinerea (Bon.). — See "Apricot." Some- 
times causing decay of late-ripening fruit in moist regions near 
the coast. Control for the fruit-rot stage recommended in Eastern 
states consists of spraying of self -boiled lime-sulfur (Formula 15A). 
The last application should be made a month or more before picking 
so that the stain will not remain on the ripe fruit. 

Leaf Curl, Exoascus deformans Fcl. — Young leaves are attacked 
and become much thickened and ruffled. Tips of shoots are some- 
times similarly affected and rarely areas on fruit. Affected tissue 
is light or highly colored; it becomes powdery white and dies early 
in the summer. Trees may be much injured by loss of foliage. 
Sprays for blight should control this, or, if blight is not present, 
only the spring application need be made. Some failures in control 
may be due to too late application of spray. 

Little Leaf. — See "Physiological Diseases," p. 57, under "Gen- 
eral Subjects." 

Peach Blight, Coryneum oeijerinchii Oud. — See also "Apricot," 
' ' Almond, " " Cherry. ' ' Buds are killed during winter, sunken round 
spots are killed in one-year twigs, and in spring a shot-hole effect 
appears on young leaves; later the twig spots gum profusely and 
gradually heal over unless the twig is killed. Very serious in interior 
valley and foothill districts in moist winters. Spray with Bordeaux 
(Formula 9), or lime-sulfur 1-10 between November 15 and Decem- 
ber 15. Repeat with lime-sulfur or Bordeaux when buds swell 
and before first blossoms begin to open. Peaches cannot be sprayed 
with these materials after the leaves appear without danger of serious 
injury. 

Powdery Mildew, Sphaerotheca pannosa var. persicae (Wallr.) 
Lev. — Young foliage becomes covered with white powder and growth 
may be checked. Large powdery white areas may appear on the fruit 
and later turn dark and check. Spray with lime-sulfur, as for leaf 
curl. Prune to thin foliage. Dust with sulfur at first indication of 
mildew and repeat as necessary. 

Rust, Transchelia punctata (Pers.) Arth. = Puccinia pruni, Pers. 
— Sometimes causes trouble in the canneries through interfering with 
peeling of fruit, small hard spots remaining in the surface. See 
"Almond," "Apricot," "Plum." 



Circular 265] PLANT DISEASE AND PEST CONTROL 37 

Black Peach Aphis, Aphis persicae-niger Smith. — A shiny black 
aphid occurring in great numbers on the young tender shoots. Spray 
with nicotine and soap (Formula 27) or dust with 5 per cent nicodust 
as soon as the insects appear. 

Black Scale.— See "Apricot." 

Branch and Twig Borer, Polycaon confertus Lee. — See ' ' Apricot. ' ' 

Brown Apricot Scale. — See "Apricot." 

California Peach Borer, Aegeria opalescens Hy. Edw. — White cat- 
terpillars attaining a length of one and one-half inches which burrow 
under the bark at the base of the trees, often extending their tunnels 
down into the bases of the main roots. Often serious, as they may 
completely girdle the trees. Dig out the worms carefully in the fall 
and spring and paint over the wounds with a good asphaltum paint. 
Use para-dichlorobenzene in summer and fall. See methods of treat- 
ment p. 80. 

Cankerworms. — See "General Subjects." 

Flat-Headed Apple Tree Borer.— See "Apple." 

Peach Rust Mite, Phyllocoptes cornutus Banks. — A microscopic 
mite causing a silvering of the leaves. Spray in winter when the trees 
are dormant or when buds swell in the spring with lime-sulfur 1-10 
to kill mites hibernating in buds. 

Peach Twig Borer, Anarsia lineatella Zeller. — A small, dark- 
reddish caterpillar, scarcely one-half inch long, which burrows into 
and kills the young tender tips of the twigs and, later on, may infest 
the fruit to some degree. The minute young forms hibernate in small 
cells in the bark and are effectively killed in the early spring of the 
year with lime-sulfur 1-10 applied just as the blossom buds begin to 
open, which is before the larvae are able to enter the expanding leaf 
buds. 

The investigations carried out by W. P. Duruz have led to the 
following more complete recommendations for the control of the 
peach twig-borer on peaches and apricots: 

1. Spray with commercial liquid lime-sulfur at the rate of 1 
gallon to 9 of water, plus basic arsenate of lead powder, 3 pounds to 
100 gallons, in the spring at the pink stage, that is, just previous 
to blossoming. This combination will control diseases and insect 
pests other than the peach twig-borer. Because of the frequent 
damage resulting from lime-sulfur in coastal districts, it is con- 
sidered best not to use this spray on apricots. Therefore Bordeaux 
mixture, 7-8-50, plus basic arsenate of lead, 3 pounds to 100 gallons. 



38 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION 

seems to be the best combination for apricots when brown rot or 
shot-hole fungus and peach twig-borer are to be controlled. This 
later spray also should be applied at the pink stage. 

2. Nicotine sulfate, % of a pint to 100 gallons of water, with 3 
pounds of soap as a spreader, is a good remedy for the peach twig- 
borer, and may be used alone in a few limited cases where diseases 
and other insects are not troublesome. This is specially recommended 
for apricot trees which may -be injured by lime-sulfur or arsenical 
sprays. 

3. A summer spray of arsenate of lead, basic or neutral (never 
acid), at the rate of 3 pounds to 100 gallons of water with % 
pounds of casein spreader, may be used as an additional insurance 
against "wormy" fruit. This spray should be applied not less 
than two weeks before the fruit is picked. 

4. Too much emphasis cannot be placed upon the necessity 
of proper spraying at the right time. It is essential to cover the entire 
surface of the tree, particularly the newer and outer portions of 
the branches. Use at least 175 pounds pressure and preferably 250 
pounds. 

5. All prunings should be collected and particularly the small 
and newer wood should be burned before spring, because this material 
harbors the larvae. 

6. Cull fruit should not be carelessly left about the orchard 
or packing house. All wormy fruit should be collected and properly 
disposed of. It should be fed promptly to pigs or other stock, or 
destroyed by burning or burying. A quick and simple manner of 
destroying worms in the cull fruit is to place the discarded fruit 
in a pile or in a trench, saturate with oil or cover with wood, and 
ignite. The heat resulting from the fire will be sufficient to kill 
the larvae in the fruit. Another means of destroying the larvae is 
to place the cull fruit in a caldron of boiling water for 15 minutes. 

Red Spider.— See "Almond" and "Prune." 

San Jose Scale. — See "Apple." 

Shot Hole Borer.— See "Apricot." 

Tent Caterpillars. — See "General Subjects." 

Wheat Thrips, Frankliniella tritici (Fitch). — This minute orange 
and yellow thrips often does considerable damage to the young fruit 
at blossoming time and later. For control see pear thrips under 
"Pear." 



Circular 265] PLANT DISEASE AND PEST CONTROL 39 

Combined Spraying 

Two applications of lime-sulfur as recommended above for peach 
blight will control all of the usual diseases and pests of the peach 
in California which can be reached by any spray treatment, but 
lime-sulfur has occasionally been reported as causing injury when 
applied in the bloom and may not be effective for control of leaf 
curl when applied late. 

PEAR 

Black End. — Is presumably a physiological disease comparable to 
blossom end rot of tomatoes. No recommendation as yet except to 
give good care, especially as to drainage. 

Black Leaf. — Resembles blight in effect; bark, however, is not 
reddish and juicy when cut into, but with dry black spots or areas. 
(See "Sour Sap," under "General Subjects.") Shallow soil and 
summer drought appear to have particular significance in connection 
with this trouble. A peculiar condition sometimes develops on indi- 
vidual trees in which dark points develop in one-year bark. These 
persist and become hard, raised and enlarged until the whole surface 
may be much roughened and hardened. In certain dry soils in the 
south a peculiar drying back of twigs occurs. The drying progresses 
to a certain point and new shoots start out below. Making the 
moisture supply of the soil more constant is believed to have greatly 
helped this condition. See "Sour Sap," p. 57. 

Blight, Bacillus amylovorus (Burr.) Detoni. — Tender growth be- 
comes watery, darkens rapidly, wilts, and dies ; usually minute beads 
of viscid material exude ; they dry in the same form and show a solid 
mass of bacteria under the microscope when moistened in water; in 
heavier bark the exudate may be more copious, or it may be lacking; 
the diseased tissue may be recognized by cutting into it. Watery, 
reddish, or somewhat dark streaked areas indicate blight. Any 
succulent part of the top, body or root may be attacked. Cut out 
all affected parts very thoroughly. Work especially on "hold-over" 
in large limbs, trunks, and roots during the winter. Disinfect tools 
and cuts freely. A new system is being largely used in which only 
the outer bark is cut away, leaving the cambium. Keep close watch 
to check new development of infection. Mercuric cyanid and corro- 
sive sublimate combined, 1 part of each to 500 of water* (Formula 

* Mr. Leonard Day of our Pomology Division recommends instead of water 
in the above formula 1 part water in 3 parts glycerine. The disinfectants are 
dissolved in the 1 part of water and the 3 parts of glycerine added. Hot water 
dissolves the chemicals more readily than cold. This spreads and penetrates 
better than the water solution. 



40 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION 

28a, p. 90), is widely used for disinfection. Keep all suckers and 
spurs off of root and body. In new plantings in blight regions, top- 
work on resistant varieties. Surprise, Ussuriensis, and others are 
being used and promise well. 

Avoid stimulating excessive and succulent growth. Clean up or 
destroy infected apple, quince, loquat, Christmas berry and related 
plants in the neighborhood. 

Scab, Venturia pyrina Aderh. = Fusicladium. — Dark, velvety 
mold patches appear on young fruit and leaves; badly affected fruit 
drops, but much remains, the dark areas becoming hard and rough and 
often cracked, deforming the fruit. Plow under all old leaves as 
thoroughly as possible. Spray with lime-sulfur 1 to 12, or Bor- 
deaux (Formula 9) just as the winter buds first loosen to show the 
individual flower buds. Repeat just before the first flowers open. 
Where there is danger of late scab infection, follow directions under 
1 ' Combined Spraying. ' ' 

Many varieties of pears are self-sterile or partly or occasionally 
so. Cross pollination is sometimes essential and perhaps always bene- 
ficial for the Bartlett. Frost may cause flowers to drop or fruit to 
develop russet areas or bands. Premature starting of blosson buds 
from unfavorable conditions may simulate thrips injury, causing 
them to be loose and dry in winter and to come out imperfectly in 
spring. Glut morceau fruit becomes injured and deformed or drops, 
apparently from cold, when others are not injured. 

Baker's Mealybug, Pseudococcus maritimus Ehrh. = P. bakeri 
Essig. — Small, oval, flat insect less than one-quarter inch long and 
covered with white powdery wax and normally with several white, tail- 
like filaments nearly half as long as the body. The egg sacs look like 
small masses of cotton. The insects occur under the bark, on the under 
side of limbs, in cracks, wounds, and in the blossom end of the fruit. 
Control measures are difficult and consist of repeated applications of 
crude carbolic acid and distillate emulsion (Formula 26a) during the 
winter months and until the buds begin to open in the spring. Scrape 
the rough bark from the trunks and larger limbs so as to expose the 
mealybugs to fhe spray. If the fruit is infested, spray during the 
summer with water under heavy pressure to wash the bugs away. 

Branch and Twig Borer. — See "Apricot." 

Brown Apricot and Other Soft Scales.— See "Apricot." 

Cankerworms. — See "General Subjects." 

Cherry or Pear Slug. — See "Cherry." 



Circular 265] PLANT DISEASE AND PEST CONTROL 41 

Codling Moth. — See "Apple." The control of this insect on pears 
is not so difficult as on apples, but thorough work is necessary to insure 
clean fruit, particularly in districts where large acreages of pears are 
grown. 

Fruit Tree Roller.— See "Apple." 

Green Apple Aphis. — See "Apple." 

Italian Pear Scale, Epidiaspis piricola Del G. — A small, gray, cir- 
cular scale, the body being dark red, usually occurring under the 
moss or old bark; but it may cover the trunks and all of the main 
branches of the tree. Causes sunken areas in old limbs and greatly 
weakens the tree. Spray in the winter months, preferably in January 
and February, with crude oil emulsion (Formula 18), distillate sprays 
(Formulas 20 to 23), or miscible oils. The crude oil emulsions are 
preferable. Thoroughly drench the limbs and trunks. (See Cir. No. 
224, Calif. Agr. Exp. Sta., Univ. Calif., Dec, 1920.) 

Pear Leaf Blister Mite, Eriophyes pyri (Pagen.). — A microscopic 
mite causing pinkish and yellowish blisters or marks on the young 
terminal leaves and occasionally reddish blotches on the young fruit. 
Spray in November or February with lime-sulfur 1-10 to kill hiber- 
nating mites in buds. 

Pear Root Aphis, Eriosoma languinosa (Hartig). — A small dark 
aphid covered wtih white cottony material and greatly resembling 
the woolly apple aphis, but attacks only the pear roots. For control 
see woolly aphis under "Apple." Eliminate young stunted trees and 
replant healthy ones. The Japanese root is much more resistant to 
this pest than the French. Use para-dichlorobenzene in fall. See p. 80. 

Pear Thrips, Taeniotlirips inconsequens Uzel. — Small, slender, 
black insect one-sixteenth inch long, appearing before or at the time 
the blossom buds begin to open and continuing until after blooming 
season. The young or white thrips work in the late blossoms, but 
chiefly on the young fruit and leaves. Spray as often as necessary 
with the government formula (Formula 24) or dust repeatedly with 
5 per cent or 6 per cent nicodust. Watch for adult black thrips as 
soon as the buds begin to open and apply control measures as soon 
as any number of the insects appear. (See Cir. No. 223, Calif. Agr. 
Exp. Sta., Univ. Calif., Nov., 1920.) 

Red Humped Caterpillar. — See ' ' Prune. ' ' 

San Jose Scale. — See "Apple." Treatment for the Italian pear 
scale above will also suffice for this insect. 



42 university of california — experiment station 

Combined Spraying 

1. For scale of any kind and for moss and a general clean-up, use 
a winter spray of lime-sulfur 1-10, crude oil emulsion (Formula 18), 
or miscible oil. 

2. For scab and thrips use Bordeaux mixture (Formula 9), or 
lime-sulfur 1-12 as cluster buds are opening, adding an extra 10 
pounds of lime and 1 pound of 40 per cent nicotine sulfate to each 200 
gallons of spray. Oil sprays should not be mixed with lime-sulfur or 
Bordeaux mixture for this purpose. 

3. For scab and thrips, repeat "2" when first blossoms are about 
to open. 

4. For codling moth and late scab infection, spray when petals are 
falling with 8 pounds of lead arsenate in 200 gallons of 1-30 lime- 
sulfur or 200 gallons of Bordeaux mixture. 

PLUM, PRUNE 

Armillaria, Wood Decay, Crown Gall, Sour Sap and Physiological 
Diseases. — See "General Subjects,'' p. 53. 

Brown Rot. — Not often serious. See "Apricot." 

Leaf Spot, Coryneum beijerinckii Oud. — See "Apricot," "Peach." 
and "Almond." 

Plum Pockets, Exoascus pruni Fcl. — This disease is as yet very 
local. Young fruits puff up early, becoming large and bladdery, 
then wither and fall. Remove all diseased fruits and twigs and burn. 
Spray as for leaf curl of peach. 

Rust, Transchelia punctata (Pers.) Arth.=^Puccinia pruni Pers. — 
Small, dark brown, powdery dots appear on the lower sides of leaves 
with corresponding yellow dots above. Not observed to be serious. 

Unfruitfulness. — See also under "Pear" and "Almond." The 
University's Division of Pomology is adding constantly to our 
knowledge of the relations of varieties for efficiency in cross fertiliza- 
tion. Growers should keep carefully posted on these results. Vari- 
eties may be wrongly chosen, bees may be lacking, premature starting 
and failure of buds may occur. 

Black Scale. — See "Apricot." 

Brown Apricot Scale. — See ' ' Apricot. ' ' 

Branch and Twig Borer. — See ' ' Apricot. ' ' 

California Peach Borer. — See ' ' Peach. ' ' 

Cankerworms. — See "General Subjects." 



CIRCULAR 265] PLANT DISEASE AND PEST CONTROL 43 

Cherry Fruit Sawfly. — See "Cherry." Also attacks varieties of 
plums. 

Citrus Red Spider, Tetranychus citri McGregor. — See "Common 
Red Spider," p. 44. 

Dried Fruit Beetle, Carpophilus hemipterus (Linn.). — A small 
black beetle less than one-quarter inch long with a reddish spot 
near the middle of the dorsum. The adults and small yellowish 
or whitish larvae feed on the dried fruit and continue to breed indefin- 
itely in storage. They may be controlled by fumigation as recom- 
mended for grain weevil. See " Grain. " 

Flat-Headed Apple Tree Borer.— See "Apple." 

Fruit Tree Leaf Roller.— See "Apple." 

Indian Meal Moth, Plodia inter punctella Hiibn. — The caterpillars 
are white or pinkish and about one inch long. They feed on the dried 
fruit, through which they work their way to all parts, leaving behind 
a trail of excrement, webbing, and spoiled fruit. Their presence is 
usually first indicated by webbing on the fruit or around the sides of 
the container. The adults are small, slender, silvery gray moths with 
the apical ends of the wings coppery. This insect is controlled in the 
same way as the granary weevil. (See " ' Grain. ") Dipping the fruit 
in scalding water prior to packing kills all forms of this insect. Small 
packages of dried fruit should be made insect proof to prevent infes- 
tation in warehouses and storerooms. 

Italian Pear Scale.— See "Pear." 

Mealy Plum Louse, Hyalopterus arundinis (Fabr.). — A pale green 
aphid covered with a fine white mealy wax ; it collects in great numbers 
on the under side of the leaves of tender shoots in May and June. 
Spray with 6 pounds of fish oil soap to 200 gallons of water, or use 
nicotine soap spray. (Formula 27.) The soap alone appears to give 
as satisfactory results as the nicotine soap spray and is much cheaper. 

Peach Twig Borer. — See "Peach." 

Pear Thrips.— See "Pear." 

Red-Humped Caterpillar, Schizura concinna S. & H. — The cater- 
pillars are beautifully lined, reddish, black and yellow with a con- 
spicuous red hump on the back. They feed in large colonies and 
may entirely defoliate individual limbs or entire trees during the 
spring and again in the fall of the year. They spin no webs and 
are not to be confused with the tent caterpillars which appear in 
the spring and the webworms, in the fall. Control measures consist 
in cutting out and burning the entire colonies when small or in 
spraying with arsenate of lead as for codling moth or better in dust- 
ing the infested trees with 1 pound of powdered arsenate of lead 



44 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION 

thoroughly mixed with 4 pounds of hydrated lime. The dusting may 
be effectively done with either a hand or power machine. 

Red Spider or Almond Mite. — See "Almond." 

San Jose Scale. — See "Apple." 

Tent Caterpillars. — See "General Subjects." 

Common Red Spider, Tetranychus telarius Linn. — This small, pale 
green or yellow mite, with from two to six dark spots on its back, 
appears in mid and late summer and does great damage to plum and 
prune trees by causing the leaves to fall prematurely. Dusting and 
spraying as recommended for the almond mite (see "Almond") should 
be done very thoroughly and continued until the first good rains occur 
in the fall. 

Tussock Moth.— See "Apple." 

Combined Spraying 

For scale, moss, and a general clean-up, spray in winter with crude 
oil emulsion. (Formula 26.) 

POTATO 

Black Heart. — Dark clouded areas appear in the flesh and may 
dry out, leaving cavities. Due to high temperature or lack of oxygen 
or the two combined. Occurs mostly in storage, but may develop 
before digging. 

Brown Streak. — Tubers show a brown ring or streaks in the flesh 
when cut into. Apparently due to climatic conditions — high temp- 
erature and drought. Affected seed may produce a healthy crop. 
See "Physiological Diseases," p. 57. 

Jelly End, Soft Rot, Leak. — Very soft or watery rots; are due 
to infection in wounds with several fungi, Pythium, Rhizopus, etc. 
Avoid injury and bruising in digging. 

Potato Late Blight, Late Rot, Phytophthora infestans (Mont.) 
De Bary. — Translucent spots appear on the leaves and stems, which 
spread rapidly till entire top is wilted and prostrate. The tubers show 
sunken spots at digging and rot in storage. Spray with Bordeaux 
mixture (Formula 9) immediately after rains. 

Rhizoctonia or Black Scurf, Corticium vagum B. and C. = Rhiz- 
octonia. — Dark, reddish-brown scabs are found on the tubers. These 
may be scraped off, leaving the surface smooth. Underground parts 
are killed in some cases, destroying plants, reducing the number of 
tubers, or causing various symptoms in the tops, sometimes with 
aerial tubers. The fungus is of widespread occurence in soil and 
attacks many plants. See ' ' Beans, " " Damping Off, ' ' p. 55, etc. 



CIRCULAR 265] PLANT DISEASE AND PEST CONTROL 45 

For tuber diseases in general secure seed from healthy fields 
and reject any tubers showing appreciable amounts of scab, rhizoc- 
tonia, wilt (as shown by dark fibres in section of the stem end) or 
other suspicious symptoms. If scab and rhizoctonia are feared, dip 
in a solution of corrosive sublimate (Formula 28, p. 90) for 1% 
hours before cutting. This solution should be placed in wooden or 
earthenware (not metal) containers and should be used only 4 or 5 
times; also the potatoes should be clean as possible before dipping. 
Do not use potatoes treated with corrosive sublimate for food. If 
only scab is feared, the tubers may be dipped in a solution of formal- 
dehyde, 1 pound to 30 gallons of water for 2 hours. The solution 
may be used repeatedly, and is not spoiled by contact with metal. 

Potato pathology in recent years has become highly intricate and 
control measures must be adapted to local conditions. Healthy 
seed, rotation of crops, preparation of soil and management are 
of great importance. See your farm advisor and authorities on 
potato culture. 

Scab, Actinomyces scabies (Thaxter) Giiss. = Oospora. — The com- 
mon rough, corky spots in the surface of tubers which are made 
unsightly. Underground parts of the growing plant are also injured 
to some extent. Said to be favored by alkaline soil, or the addition 
of lime or manure in excess, and retarded by the plowing down of 
a green cover crop. Use clean seed and dip in a fungicide. See 
' ' Rhizoctonia. ' ' 

Wilt and Dry Rot, Fusarium sp. — Plants are affected as in severe 
drought, the leaves ripening prematurely. Tubers appear sound, but 
often show a ring of darkened fibres when the stem end is cut across. 
Low temperature in general retards rot associated with wilt. So 
far as possible, use seed from healthy fields. 

Aphids (Various Species). — Dust thoroughly with 5 per cent nico- 
dust or spray with 1 part of 40 per cent nicotine sulfate to 800 parts 
of water. 

Armyworms and Cutworms. — See "General Subjects." 

Flea Beetles and Leaf Beetles. — See "Melon." Use Bordeaux 
mixture (Formula 9) as a repellent, or a nicodust lead arsenate 
mixture. 

Garden Nematode or Eelworm. — This microscopic round worm 
produces a pimply or warty surface on the potato and small brown 
dots just beneath the skin. Plant only clean seed and avoid infested 
soil. 

Grasshoppers. — See "General Subjects." 

..... 



46 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION 

Potato Stalk Borer, Trichobaris trinotata Say. — The larvae are 
small, pale yellow or white, and not over one-half inch long ; they bore 
throughout the middle of the stalks, causing them to wilt and die. 
The adults hibernate in the old dry stalks, which should be raked up 
after digging and burned. This affords an almost perfect control if 
thoroughly done. 

Potato Tuber Moth, Phthorimaea operculelld (Zeller). — The full- 
grown caterpillars are white or pinkish and not over three-quarters 
inch long. They make numerous burrows just under the skin and 
throughout the tubers, continuing to work as long as the tubers are 
available. Infestation may occur in the field or in storage. Hill up 
well around the growing plants and remove the potatoes as soon as 
dug to prevent infestation in the field. Store in a clean, uninfested 
place. If infested, fumigate with 20 to 30 pounds of carbon bisulfid 
to every 1000 cubic feet of air space at a temperature 70° F. or over. 
Plant only clean seed. 

Tomato and Tobacco Worms. — See "Tomato." 

Wireworms. — See "General Subjects." 

Combined Spraying 

Bordeaux mixture will control not only the flea beetles but will 
materially aid in subduing many fungus diseases. 

PUMPKIN. See "Melon" 

ROSE 

Cold Injury. — Many plants are found in spring with dark-stained 
leaves or small distorted and sickly foliage, due to chilling of tender 
tissue of shoots, which start growth too early in winter. Delay 
pruning until February or later. Prune rather heavily and stimulate 
vigorous growth by general culture measures. 

Mildew, Sphaerotheca pannosa (Wallr.) Lev. and S. humuli 
(D. C.) Burr. = Oidium. — White, powdery mildew spreads over 
young stems or leaves, causing distortion or dropping of leaves and 
discoloration; severe in cool coast districts. Spray with lime-sulfur 
1-10 before the spring growth starts. Use dry sulfur, sulfur paste, 
or lime-sulfur 1-35 when disease first appears. 

Aphids (Various Species). — Two common aphids usually infest 
roses: the large green and pink Macrosiphum rosae (Linn.), which 
commonly attacks the tender tips and buds, and the small green 
Myzaphis rosarum (Walk.), which works on all parts of the plant and 
produces large quantities of honey dew, resulting in the smutting of 



CIRCULAR 265] PLANT DISEASE AND PEST CONTROL 47 

the plants. Both may be effectually controlled by dusting liberally 
with 5 per cent nicodust, by spraying with nicotine sulfate, 40 per 
cent, 1 part to 1000 parts of water, or by thoroughly hosing off the 
plants every two or three days with a strong water pressure and a 
coarse nozzle. 

Fuller's Rose Beetle.— See "Citrus Fruits." 

Raspberry Horntail. — See ' ' Bush Fruits. ' ' 

Rose Scale. — See ' ' Bush Fruits. ' ' Spray infested portions of the 
plants during the winter months with miscible oils. 

Rose Snout Beetle, Bhynchites bicolor Fabr. — A small red and 
black snout beetle, scarcely one-quarter inch long, which punctures 
the buds of roses, causing numerous holes in the petals when the 
flowers open. Jar beetles in pan of oil in the early mornings. A 
10 per cent nicodust has given good control in some places. 

Combined Spraying 

For fungus diseases and aphids, a 40 per cent nicotine sulfate may 
be added to sulfur sprays as given above, and a sulfur nicodust may 
also be used for mildew and aphis. 

SNAPDRAGON 

Rust, Puccinia antirrhini D. & H. — Brown rust sori break out 
through the leaf and stem. Infection is usually heavy and the plant 
becomes unsightly and dies. Water and fertilize freely to stimulate 
growth. When the disease becomes severe destroy badly affected 
plants and clean up thoroughly in the fall. Start with clean seed- 
lings. Pentstemon is a fairly good substitute for snapdragon, and 
does not rust. 

Aphids. — Dust thoroughly with 5 per cent nicodust. 

SORGHUM, SUDAN GRASS, AND BROOM CORN 

Head Smut, Sphacelotheca reiliana (Kuhn.) Clint. — Whole head 
or panicle becomes a black mass. Method of treatment not yet 
developed. Affected plants should be destroyed at first appearance. 
Affects also corn. 

Kernel Smut, Sphacelotheca sorghi (Lk.) CI. — Kernels form en- 
larged grains which become fragile and filled with a black powder. 
Controlled by seed treatment. See ' ' Grain. ' ' 

Aphids (Various Species). — See "Grain." 

Armyworms and Cutworms. — See "General Subjects." 

Granary and Rice Weevils. — See "Grain. 

Grasshoppers. — See "General Subjects. 



t •> 



48 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION 

SPINACH 

Armyworms and Cutworms. — See "General Subjects.' ' Poison 
bran mash sown broadcast over the fields has proved very success- 
ful in completely protecting young plants. 

Beet or Spinach Leaf Miner, Chortophila hyoscyami Panzer. — 
Small white maggots mining the leaves and causing discolored areas. 
Keep down all weeds about the fields, burn refuse tops, harvest as 
early as possible. Winter-grown spinach usually escapes the attacks 
of this insect. 

Flea Beetles. — See ' ' Cucumber. ' ' 

Grasshoppers. — See ''General Subjects." 

Melon Aphis.— See " Melon." 

SQUASH. See Melon. 

STRAWBERRY 

Leaf Spot, My cosphaerella frag ariae (Tul.) Linn. = Ramularia. — 
Dead spots on leaves, one-quarter inch or less in diameter with red 
borders; if abundant it lowers the vitality of the plants. Clean up 
and burn the leaves in late fall. Spray with Bordeaux mixture 
(Formula 9) if the disease becomes serious. 

Leaf and Stem Rot. — Symptoms are those of acute drought injury ; 
plants die back in hot weather and inferior growth comes up later with 
poor production; roots are killed off, apparently by poor soil condi- 
tions. Use less water. Improve drainage. Wash out alkali in winter 
by flooding. 

Gray Mold, Botrytis rot.— See "Bush Fruits." 

Strawberry Aphis, Myzus fragaefolii Ckll. — A very small pale 
yellow aphis occurring in great numbers on the under sides of the 
leaves, and often smutting the foliage. Defoliate the plants in winter. 
Dust liberally with 5 per cent nicodust as soon as the aphids appear, 
applying it to the under side of the leaves with an upturned discharge 
pipe. 

Strawberry Crown Moth, Aegeria rutilans H. Edw. — A white cat- 
erpillar one-half inch long or less boring into the crown of the plant, 
causing it to turn yellow and die. Remove and burn infested plants 
as soon as discovered. Be sure of clean nursery stock. 



Circular 265] PLANT DISEASE AND PEST CONTROL 49 

Strawberry Flea Beetle, Haltica ignita Illiger. — A bright metallic, 
golden, green, or purplish flea beetle, one-sixth inch long, feeding upon 
the leaves of the plants. Use Bordeaux mixture (Formula 9) as a 
repellent. 

Strawberry Leaf Beetle, Paria canella (Fabr.). — A small brown 
beetle with black markings on the dorsum and averaging one-eighth 
inch long. The adults eat numerous small irregular holes in the 
leaves, while the small white larvae attack the roots. It is a severe 
pest, and should be eradicated, if possible, by destroying all infested 
vines and thoroughly sterilizing the soil by steam or carbon bisulfid. 
Established infestations may be reduced by thoroughly spraying with 
arsenate of lead (Formula 2), or by dusting with 1 part of basic 
powdered arsenate of lead to 4 parts of powdered hydrated lime. 

Strawberry Root Weevil. — The one known infestation of Otio- 
rhynchus rugifrons Gyll. in California is quarantined. Secure plants 
from uninfestated district. Report any suspicious cases to the State 
Department of Agriculture, Sacramento, Calif. 

Two-Spotted Mite, Tetranychus telarius Linn. — See "Bean" and 
1 ' Prune. ' ' Though ordinarily controlled with dry sulfur, this method 
cannot be used on strawberries because of the severe burning to the 
foliage. Very small amounts of sulfur in the ditches between the rows 
have afforded some relief. 

SWEET POTATO 

Black Rot, Sphaeronema fimbriatum (E. & H.) SdLQe.=Ceratocystis. 
— Black spots appear on sprouts and circular black spots on surface 
of potatoes, with tissue below greenish. Affected potatoes are bitter 
when cooked. Spreads in storage. See "Wilt." 

Foot Rot, Plenodomus destruens Harter. — Brown to black spots 
appear on stems near surface of soil late in season and plants finally 
wilt, usually not producing potatoes. Also a brown firm rot of pota- 
toes often starting in wounds. See "Wilt." 

Scurf, Monilochaetes infuscans E. & H. — A brown discoloration or 
spotting occurs on the surface of the potatoes rendering them less 
attractive and more liable to dry out in storage. See ' ' Wilt. ' ' 

Soft Rot, Rhizopus nigricans Ehr. — Mainly a storage trouble; rot 
starts at injuries and progresses rapidly; decayed part becomes cov- 
ered with white mold which later turns black. Avoid bruising. Dry 
well before storing. For long keeping, pack in dry sand. Moisture 
and temperature requirements of sweet potatoes in storage are differ- 
ent from those of most other products and must be carefully observed. 



50 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION 

Wilt or Stem Rot, Fusarium sp. — Leaves become paler than nor- 
mal; plants wilt and die; stems have the fibres blackened and this 
shows also in the stem end of the potato as a blackening when cut 
across. 

Stem and root diseases of sweet potatoes require siviilar treatment. 
Hotbeds which have been used previously for sweet potatoes should 
be cleaned out and soaked with formalin 1 pound to 30 gallons of 
water. The soil used should be from some place where sweet potatoes 
have never been present or should be disinfected. (See p. 95.) The 
manure should have no remains of sweet potatoes in it. Plants and 
potatoes are both infectious. Where wilt is present, select seed pota- 
toes in the field before frost, cutting across the stems and rejecting 
all hills which show black rings. Store all seed potatoes separate from 
the main crop, where contamination may not spread to them. Where 
diseases are serious, dip the seed in corrosive sublimate as for white 
potatoes (see p. 45), except that the time of soaking must not exceed 
5 to 10 minutes. Where diseases become troublesome, rotate crops, 
planting no sweet potatoes for three to six years. 

TOBACCO. See "Tomato" 

TOMATO. See also ' ' Potato ' ' 

Blossom End Rot. — Dry spot appears at blossom end of green fruit 
and develops slowly. Avoid drought or irregular irrigation. 

Damping-off. — See "General Subjects." 

Fruit Decays. — In California due mostly to common molds which 
gain access in some mechanical injury and develop on the way to 
market. Remove all refuse fruit to a safe distance from the packing 
house. Avoid mechanical injuries in the fruit. 

Late Blight, Late Rot, Phytophthora infestans (Mont.) De B. — In 
late moist weather large vague spots appear on the leaves, at first dark 
and watery, becoming slightly frosted with emerging fungus threads 
below, then deteriorating rapidly. Similar spots appear on the fruit, 
not well-marked at first, but the fruit spoils rapidly. Spray with 
Bordeaux mixture (Formula 9) immediately after rains. 

Western Blight. — Plants become pale; leaves roll upward, expos- 
ing purplish veins; plants become worthless and most of them die. 
No control has been developed as yet. 

Wilt, Fusarium sp. — Plants in the field turn yellow and die often 
after reaching considerable size. A dry rot is found in the stem 
and roots. Secure clean soil for seedbed or disinfect soil and beds. 
(See p. 95.) Rotate crops. Resistant varieties are being sought. 



Circular 265] PLANT DISEASE AND PEST CONTROL 51 

Armyworms and Cutworms. — See " General Subjects." 

Grasshoppers. — See "General Subjects.' ' 

Darkling Ground Beetles, Blapstinus sp. and Eurymetopon bicolor 
Horn. — Small, dull black or bluish-black beetles, scarcely more than 
one-quarter inch long, living in the soil and responsible for much dam- 
age to young plants shortly after transplanting. Before resetting, 
wrap the stems of the young plants from roots to tops with tissue paper 
so as to have three or four thicknesses for protection, or scatter poison 
bran mash (Formula 4) over the ground at planting time. 

Flea Beetles. — Dust with powdered arsenate of lead, 1 part to 4 
parts of dry lime or sulfur, nicodust and arsenate of lead, or spray 
with Bordeaux mixture. (Formula 9.) 

Garden Nematode. — See "General Subjects." 

Tomato Worm, Protoparce sexta, Joh. and Tobacco Worm, P. 
quinquemaculata Haw. — Large green worms often attaining a length 
of four inches. They strip the leaves from the vines. The adults 
are known as humming bird moths because of their large size and 
swift flight. They are gray with yellow spots on the sides of the 
body and have a wing expanse of 4 or 5 inches. The caterpillars 
may be controlled by hand picking, i.e., cutting the worms in two with 
a pair of scissors, or by dusting the vines with 1 part of powdered 
arsenate of lead to 4 parts of finely ground hydrated lime. 

WALNUT 

Blight, Pseudomonas juglandis Pierce. — Young tender parts are 
attacked. Spots at first watery, soon turning black, often spread and 
kill young nuts, leaves, or tender tips of shoots. No specific remedy. 
Give the trees the best possible care. Thin out the tops of the old trees. 
Control aphis. Plant resistant varieties. 

Crown Gall, Wood Decay, Armillaria. — See " General Subjects." 

Melaxuma, Dothiorella gregaria Sacc. — Black sunken cankers de- 
velop on larger limbs and trunks; the limb may be girdled and the 
part above die. Cut out diseased bark areas and apply Bordeaux 
paste. 

Winter Killing. — Irrigate about November 1, if no good rains have 
fallen. Whitewash trunks in the fall. Do not irrigate after August, 
except as above. 

Codling Moth, Cydia pomonella (Linn.). — See "Apple." This 
worm feeds on the green husks or usually bores directly into the kernel 
of the walnuts before they are mature, and also often works its way 



52 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 

into the kernel after the shell becomes hardened by making an en- 
trance in the suture at the base. It may be controlled by spraying 
with basic arsenate of lead or by dusting with powdered basic arsenate 
of lead and hydrated lime when work on husks of nuts is first observed 
in the spring — May, June, or July — depending upon climatic condi- 
tions due to location near the coast or inland. Consult local horti- 
cultural officials. 

Frosted Scale, Lecanium pruinosum Coq., and Cherry or Calico 
Scale, L. cerasorum Ckll. — Same control as for brown apricot scale. 
See "Apricot." 

Indian Meal Moth. — Attacks walnuts in storage. See "Prune." 

Nautical Borer, Xylotrechus nauticus Mann. — The borers are small, 
fleshy, white or yellowish grubs, with slightly enlarged anterior end, 
and about three-quarters inch long. The adult beetles are one-half 
inch long, dark with narrow broken yellow or whitish cross bands on 
the elytra. The larvae work in the small twigs, limbs, and trunks of 
both healthy and sickly trees. Cut out and burn all infested portions. 
Destroy all dead oaks or prunings in the neighborhood to eliminate 
breeding places. 

Red Humped Caterpillar. — See "Prune." 

Two-Spotted Mite. — See "Prune." Dust thoroughly with dry 
sulfur. 

Walnut Aphis, Chromatins juglandicola (Kalt.). — A small pale 
yellow aphis occurring in great numbers on the under sides of the 
leaves and producing great quantities of honey dew, which causes 
severe smutting of the foliage. Dust thoroughly with a 2 per cent 
nicodust during last week of May or the first part of June. Some- 
times a second application is necessary in July or August. 

Walnut Blister Mite, Eriophyes erinea Nalepa. — A microscopic 
mite producing yellow or brown felt-like galls on the under sides of 
the leaves. It is not a serious pest, but may be cleaned up by spraying 
trees with lime-sulfur 1-10 in the spring when the buds are swelling. 
Control measures are not recommended except in extreme cases. 

Yellow-Necked Caterpillar, Datana ministra Drury. — A black, 
hairy caterpillar with numerous longitudinal yellow stripes on the 
back and sides and a yellow or orange-colored neck. It averages about 
two inches in length and is closely related and similar in habits to the 
red-humped caterpillar, and may be handled in the same way. See 
same under "Prune." 

WATERMELON. See "Melon" 
WHEAT. See "Grain" 



Circular 265] PLANT DISEASE AND PEST CONTROL 53 



GENERAL SUBJECTS 



ARMILLARIA ROOT ROT (OAK FUNGUS), Armillaria mellea 

(Vahl) Quel. 

Caused by a native fungus which lives saprophytically and para- 
sitically in roots of woody plants. Trees and bushes are killed in 
spots, which enlarge year after year. Affected trees fail gradually 
from diseased side or die suddenly in summer. Under the affected 
bark of roots there is a yellowish white fan-shaped mycelium which 
progresses into live bark. Black shining root-like strings (rhizo- 
morphs) grow out from old rotting roots. The wood decays with a 
uniform white rot. Large tan-brown toadstools (edible when cooked) 
arise from old infections, October to February. Surgery as in crown 
gall or pear blight can sometimes be practiced on roots and crowns 
of trees not too far gone. Black walnut, French pear, and fig roots 
are practically immune. Myrobalan is more resistant than most stone 
fruits and something may be gained by working high on this stock. 
Similarly the Delicious apple on its own roots is being tried, especi- 
ally for Gravenstein, which seems to be unusually susceptible. 
Annual fibrous rooted plants are rarely injured. Affected areas 
in orchard may be isolated by opening a trench 3 to 4 feet deep 
around them. This may be filled immediately if reopened every two 
years to keep the roots cut off. Nursery should not be planted in in- 
fected soil. 

ARMYWORMS AND CUTWORMS 

General Life History. — The adult members of this family Noc- 
tuidae) are practially all night-flyers. The caterpillars of many are 
known as armyworms and cutworms and are among the most destruc- 
tive of insect pests. They often advance from field to field in great 
numbers, like an army, devastating as they go. Like the grasshoppers, 
they attack practically all kinds of plants, including field and truck 
crops, vineyards and orchards, as well as flowers and weeds. 

The adults lay their eggs in spring and the larvae become exceed- 
ingly numerous in early summer, when most of the damage is done. 
The pupal stage is passed under ground, the light or dark brown naked 
chrysalids being housed in small earthen cells. There are several 
broods a year. The winter is usually spent in the pupal stage, but 
some larvae as well as adults hibernate. A hibernating larva often 
seriously injures grapevines in the spring by eating the buds. 



54 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 

Control. — The control of these insects has been a difficult problem 
for years, and even today the methods worked out do not always give 
relief. 

Clean culture in fall and thorough plowing of infested fields to 
kill the hibernating pupae in the cells is supposed to greatly reduce 
the next year 's broods. This has been recommended as especially im- 
portant in pea fields and gardens. 

When the worms begin to march trenches may be plowed across 
and ahead of their paths with a perpendicular wall in front of the 
advance. The worms, not being able to cross, will gather in great 
masses in these trenches and can be easily killed by spraying with 
crude oil or by crushing them with a narrow disk or roller. Arsen- 
ical sprays applied as soon as the larvae begin to appear will some- 
times materially aid in protecting crops like potatoes, tomatoes, young 
trees, grapevines, etc., but are seldom practical for forage crops. 

Poisoned baits (Formulas 4 and 5) sown in the infested fields will 
kill countless worms, and these afford by far the most satisfactory 
means of killing these insects under all conditions. In fields, pastures, 
orchards, and gardens, the poisoned baits may be freely sown over the 
plants. The armyworms and cutworms will eat the bait in preference 
to growing vegetation. 

Light traps are also used to capture the adults, but these have never 
seemed to greatly lessen the attacks, because large numbers of the 
moths captured have previously laid their eggs. 

Natural Enemies. — By far the most important factors in the con- 
trol of armyworms and cutworms are natural enemies. The parasitic 
tachinid flies kill countless numbers of them. Hymenopterous para- 
sites of the family Ichneumonidae also prey upon the young. The 
predaceous ground beetles of the family Carabidae devour the worms 
and destroy great numbers. That armyworms and cutworms are not 
injurious every year is undoubtedly due to the work of these natural 
enemies. 

CANKERWORMS 

Small green or dark measuring worms less than an inch long, which 
feed upon the leaves and young fruit and drop down on a silken thread 
when the tree is jarred. The females are wingless and crawl up the 
trees in the fall or spring to lay their eggs on the limbs and small 
branches. Egg-laying on the trees is prevented by placing tanglefoot, 
cotton, or permanent wire screen bands around the trunks of the trees 
in the fall in order to catch both the fall and spring forms. The cater- 



Circular 265] PLANT DISEASE AND PEST CONTROL 55 

pillars are easily jarred from the trees, but will crawl up again if not 
obstructed. Spraying with arsenate of lead (Formula 4) will also 
give control. 

CROWN GALL, Bacterium tumefaciens S. & T. 

Rounded fleshy to woody tumors form on roots or sometimes on 
above-ground parts, usually starting from wounds, persisting and 
growing at the edges from year to year, often girdling or causing the 
tree to break off. For nurseries, avoid old vineyard, orchard, or berry 
land which has been seriously infected. Throw out all affected nurs- 
ery trees. The clean trees in a lot having a large percentage affected 
are of doubtful value. In orchards, occasionally examine crown and 
main roots, especially of stunted trees. When not too far advanced 
this disease may be controlled by chiseling out the galls, removing 
all abnormal tissue to healthy bark and down to sound wood, steriliz- 
ing with corrosive sublimate (Formula 28 or 28a), and covering the 
wounds with Bordeaux paste or asphaltum. The trees must be gone 
over again after vigorous growth has been going on for several weeks 
and the new galls which arise at the wound margins treated. Rein- 
spection is essential. Badly affected and stunted trees should be 
pulled out and replanted, using fresh soil. 

DAMPING-OFF 

Young seedlings rot at or below the surface of the ground and fall 
over or wilt. Many may die before emerging. Cause, various soil 
fungi, Pythium, Rhizoctonia, Fusarium, and others. Best controlled 
by skill in watering. Water the plant beds only in the morning and 
on bright days. Do not sprinkle oftener than necessary. In green- 
houses or frames give plenty of ventilation. In making citrus seed 
beds put an inch or two of dry sand on the top of the soil. Some 
forms of damping-off may be prevented by soil disinfection. See 
p. 95. Where damping-off has started, spraying the plants and 
ground with Bordeaux may do some good. 

FROST AND COLD INJURY 

With yonug citrus trees in frosty localities, wrap the trunks with 
corn or milo stalks in winter. Heap up earth around the butts. En- 
close tender valuable young trees with burlap covers. For bearing 
groves obtain detailed information about methods and appliances for 
smudging with oil fuel. (See also Sour Sap.) Many plants are in- 
jured and disfigured by cold at critical stages of development, even 
when it is not cold enough to kill or even noticeably injure them at 
the time. 



56 UNIVERSITY OP CALIFORNIA — EXPERIMENT STATION 



GRASSHOPPERS 

Scatter poison bran mash or citrus bran mash freely (Formula 4 
or 5). Be sure to mix the bran and poison thoroughly. Scatter in 
alfalfa fields about 4 o'clock in the afternoon and around orchard 
trees or other plants early in the morning. 

GUMMOSIS 

Gum formation in itself is not due to any one specific disease, but 
may be brought about by many different causes. In stone fruit and 
citrus trees gumming is simply a symptom of distress, which may be 
due to specific infections or various other causes, such as unsuitable 
soil, poor condition of soil, sunscald, excess or lack of water, frost, 
or attacks of parasites. Treatment must vary according to cause. 
Badly gummed branches may be removed, gummy diseased areas of 
bark cut out, and the wounds treated as in citrus gummosis. Splitting 
the bark is useless and often harmful. 

NEMATODE (EEL WORM) 

Microscopic worms of several species penetrate the tender tissues 
of plants. The garden nemotode (Heterodara radicicola Greef.) causes 
rounded irregular fleshy swellings or root knots on tender roots. If 
abundant, the roots may become much distorted and swollen, growth 
stops, and early rotting off follows. 

Do not attempt to grow susceptible crops on infested soil. Keep 
such areas clean cultivated in summer or in a cereal crop. Grain may 
be grown in winter. Almost all important crops, except cereals and 
some fruit trees, are attacked by the garden nematode. The beet 
nematode (H. schactii Schmidt) attacks some other plants, and where 
it occurs careful rotations should be followed with total exclusion of 
beets for many years. Alfalfa is not seriously affected by the com- 
mon species, but carries it over to future crops. Alfalfa may be 
safely planted on beet nematode soil. Nematodes are worse on sandy 
soils. 

Soil intended for greenhouse use should be taken from places 
where nematodes do not occur. The absence of nematodes is best 
determined by examining growing plants such as figs, peaches, melons, 
tomatoes, or nearly any soft-rooted vegetables. Where it is not possi- 
ble to get soil which is certainly free, it should be sterilized. See 
p. 95. 

Nematodes are frequently distributed in potatoes and rooted 
plants. 



Circular 265] PLANT DISEASE AND PEST CONTROL 57 



PHYSIOLOGICAL DISEASES 

(Little Leaf, Exanthema, Die-Back, Mottled Leaf, Rosette, Bitter Pit, 
Dry Rot, Blossom-End Rot) 

Diseases of a specific nature of which the cause is not known and 
of which the symptoms seem unlike the usual effects of unfavorable 
conditions or parasites. Most of these troubles show a relation to soil 
conditions and occur especially in dry, sandy, gravelly, or hardpan 
soils, those very deficient in humus, or under conditions of irregular 
soil moisture. Trees standing over old barnyards or corrals or where 
excessive amounts of manure have been applied are also likely to show 
some of these troubles. The most promising methods of treatment are 
increasing the humus content of the soil by means of green manure 
crops and mulches, breaking up all hardpan and plow-soles, more care- 
ful irrigation to insure the maintenance of a proper and uniform 
moisture condition of the soil down to a depth of several feet and 
throughout the season until rains occur, and planting alfalfa in orch- 
ards where plenty of water is available. The soil in areas where these 
troubles occur should be examined for alkali or other injurious sub- 
stances. Where any of these diseases are serious and persistent it may 
be better to grow some other crop than to keep on with one which is 
seriously affected. 

SLUGS AND SNAILS 

May be controlled to some extent by thoroughly dusting finely 
powdered hydrated lime over the infested plants, but recent investi- 
gations have shown that a 5 per cent nicodust is very effective in kill- 
ing these pests if applied late in the evening or on dull days when the 
animals are at work on the plants. Trapping by means of boards or 
wet sacks and killing those taking shelter thereunder is effective in a 
small way. 

SOUR SAP, WINTER INJURY. Also see ' ' Sunburn ' ' 

All the ordinary forms of sour sap are due to extreme variations in 
temperature. Differences in the effect upon individual trees or orch- 
ards are due to differences in condition and susceptibility of the trees, 
produced mostly by variation in the moisture condition of the soil. 
Do not force growth late in summer. Irrigate, if possible, about No- 
vember 1, if no heavy rain has fallen. Whitewash bodies of trees 
early in November. Sour sap seems to be associated with hardpan 



58 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION 

or periods of surplus water in the soil. Good drainage should be 
emphasized. A furrow may be opened in early winter on either side 
of the tree row to carry off surplus winter rains and prevent the 
soil from remaining saturated for prolonged winter periods. Num- 
erous instances have been observed where open irrigation ditches 
have drained adjacent tree rows during the winter. Trees in the 
drained soil have escaped sour sap while those farther from the ditch 
in soil saturated with winter water have suffered badly. 

Wood Decay Prevention, Treatment of Pruning Cuts and Wounds. 
— It is doubtful whether any application on wounds materially assists 
healing except for some delicate plants like roses, where the cut stem 
may dry out. Treatment is to prevent infection with spores of wood 
decay fungi, which may be carried by wind, rain or otherwise, and be 
protected in cracks or rough places in dry wood or bark until moist 
weather, when they grow and penetrate the wood, causing rot. At 
some seasons bark knocked off may be renewed over the whole surface 
if undisturbed, or the bark may be replaced and held firmly and again 
grow on. Usually a wound must heal from the edges. The greatest 
danger comes from cracks in the heartwood, from rough breaks and 
from the "heel" at the bottom of a bad cut in which the bark nearly 
always dies back. Proper training of trees from the beginning to 
avoid narrow pinching joints and subsequent splitting is important. 
Treatment should be prompt, since when decay is established no dis- 
infectant can be expected to penetrate far enough to destroy the 
active fungus in the wood. Make a clean cut, trimming the bark 
down smoothly to sound tissues around the edges. In the case of 
branches, make a close cut, leaving no projecting stub. Thoroughly 
cover the wound with Bordeaux paste (Formula 10), and when well 
dried cover with grade D asphaltum put on in a melted condition. 
Go over the work occasionally, especially in summer or early fall, 
and renew the application of asphaltum until the wound is entirely 
healed. Bordeaux mixture may retard the formation of callus. Some 
prefer to paint the whole wound at once with hot asphaltum. Others 
prefer to use the asphalt paint cold, but this should be done with 
care to keep cracks in the wood thoroughly covered. Some 
asphaltums, especially the cold paints, have caused injury. Where 
wounds have stood for some time before covering, it would be well 
to wet the dry wood with a solution of corrosive sublimate, 1 part 
in 500 parts of 50 per cent alcohol (V4 ounce in 1 gallon). See p. 90 
for precautions in using corrosive sublimate. 

For tree surgery methods, send to Superintendent of Documents, 
Washington, D. C, for Farmers' Bulletin No. 1178, price 25 cents. 



Circular 265] PLANT DISEASE AND PEST CONTROL 59 



SUNBURN 

Whitewash bodies in fall as well as spring. Shape the trees so that 
their trunks are shaded. Cut young trees back well before planting. 
Shade trunks with shakes or protectors. Do not allow trees to suffer 
from drought. 

Tests show that the coloring matter in the bark of the trunk and 
exposed main limbs absorbs heat enough on sunny days in winter to 
raise the temperature of- the growing layer 35° to 40° F. above the 
temperature of the air. As soon as the sun goes down the tree cools 
rapidly to atmospheric temperature, which may be freezing or below. 
Whitewash reflects the heat, so that the growing layer does not get 
warmer than the air ; the cells remain dormant during the day, and are 
not injured by low temperatures at night. The above also applies in 
opposing sour sap. 

TENT CATERPILLARS 

Gray or brown, hairy caterpillars with row of white spots on back 
or pale bluish lines on sides, measuring from 1 to 3 inches long. They 
either live in compact colonies or in tightly woven webs or tents which 
are conspicuous on the trees. Entire colonies may be exterminated by 
cutting off or burning with a torch. Those on the trunks and large 
limbs may be killed by spraying with kerosene or concentrated oil 
emulsions. The small dark egg masses encircling the smaller limbs 
may be pruned out when the trees are dormant and burned. Spraying 
with arsenate of lead (Formula 1 or 2) will control the caterpillars 
effectually. 

WIREWORMS 

Wireworms get their name from their smooth, round bodies, which 
are usually shiny, varying in color from pale yellow to dark brown. 
The common injurious forms are about one inch long. They live in 
the soil, preferring sandy loams rather than heavy soils, although they 
may be found in either. The larval stages last from 1 to 3 years, so 
that to be effective control measures must cover the maximum period. 
The adult beetles are known as ' ' click beetles ' ' because of their ability 
to jump in the air with a clicking sound. They are mostly inconspicu- 
ous beetles of various shades of brown or entirely black, about one- 
half inch long. They are active and fly freely. 

Control measures are difficult because of the underground habits 
of the larvae, and as yet have not been satisfactorily worked out for 
the different species. Clean culture and crop rotations are the most 



60 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 

reliable practices, while much good comes from thorough cultivation. 
Trapping the adults with small piles of straw and burning them in fall 
and winter destroys large numbers. Replanting is often necessary 
with many crops such as potatoes, beans, peas, melons, etc. Some con- 
trol is claimed from scattering poison bran mash (Formula 4) over the 
surface of the ground. 

HOUSEHOLD PESTS 
AND ANIMAL PARASITES 

Ants. — Ants are not only serious household pests but do harm 
in the garden and orchard by distributing plant lice, scale insects, 
and other honeydew producing insects, and protecting them from 
parasitic enemies, which would otherwise destroy great numbers of 
these pests. 

The ordinary small house ants, which give off a pungent char- 
acteristic "ant" odor when crushed, are best controlled by using 
various strong arsenic and syrup poisons sold as ' ' ant poisons. ' ' The 
Argentine ant, which gives off no characteristic odor, is controlled 
by a very weak arsenate and syrup poison which is carried to the 
young by the workers and which gradually kills out the whole colony. 
For this pest use Formula 7 or 8, or buy special Argentine ant poison. 

Home-made containers for the latter poison may be made by punch- 
ing small holes around the tight-fitting tops of cans and then dipping 
in hot paraffine to prevent rusting. A sponge is placed in the bottom 
and thoroughly wet with the poison, the lid is securely fastened, the 
container marked ' ' Poison ' ' and then hung up under or in the house, 
or in the gardens or orchards, away from the reach of children. Small 
fruit jars with holes punched in the lids may be used instead of cans, 
and if screwed very tightly are less likely to be opened by children. 

Bed Bugs. — These insects lay their eggs in cracks and crevices 
about the furniture and room. They will withstand months of starva- 
tion. Heating the rooms infested to 120° F. for 12 to 24 hours is 
a satisfactory method of control where practical. Fumigation with 
cyanid is effective. Careful washing with corrosive sublimate 1-500 
(1 ounce to 4 gallons of water) of all objects and crevices is a 
substitute if the other methods cannot be used. Care should be 
taken not to wet the hands or body in solutions of this strength. 
Live steam if available is effective when applied to bunks, crevices, etc. 

Cockroaches. — Can best be controlled by mixing sodium fluorid 
(commercial) with flour in equal proportion and scattering it heavily 
along the shelves or corners frequented by the insects. 



Circular 265] PLANT DISEASE AND FEST CONTROL 61 

Clothes Moths. — These insects damage fur and woolen goods by 
the feeding of their larvae. Careful brushing and airing of stored 
materials at frequent intervals is the best protection for garments 
infrequently used. If stored over long periods, they should be care- 
fully brushed, placed in tight boxes and the covers sealed with gummed 
paper. Fumigation with carbon bisulfid or carbon tetrachlorid is 
effective in heavily infested quarters. Moth balls, cedar chests, etc., 
are effective but will not kill larvae that are already present in the 
materials. 

Fleas. — The presence of fleas is closely correlated with the presence 
of domestic animals or pets. They lay their eggs on these hosts. 
There hatches from these eggs which have dropped to the ground 
or floor, a maggot-like larva which lives on nitrogenous material until 
it changes into a mature flea. Domestic pets should be frequently 
dusted with fresh pyrethrum powder or washed in heavy suds of 
naptha soap. Mats should be provided for pets to sleep on if per- 
mitted in the house and these regularly shaken over an open fire. All 
animals should be excluded from the basement. Floors should be 
mopped with "dry" mops moistened in kerosene. Napthalene flakes 
spread over the floor of a room, allowed to remain for a few hours 
and then brushed into another room prove effective in severe out- 
breaks. For sticktight flea see Circ. 251. 

Flies. — Life History. — The common house fly lays its eggs on 
freshly deposited manure heaped in piles, also on heat-producing 
piles of vegetables and animal matter. These hatch in about two 
days into tiny glistening white, footless maggots that grow rapidly 
for approximately a week until about half an inch in length, when 
they migrate from the moister part of the manure to a drier portion ; 
here they turn into brown, barrel-shaped "pupae," from which they 
emerge as full-grown flies in about four days. 

The blow flies, flesh flies, buzz flies, or meat flies, as they are 
variously called, will also breed in manure and garbage, but prefer 
the bodies of dead animals left exposed on the ground or buried in 
shallow holes. 

When garbage is fed to animals or left exposed, unless extra pre- 
cautions are taken, fly breeding will occur in the garbage itself and 
even in moist soil that has become saturated with liquid food material, 
urine and feces. 

Manure should be removed at intervals of less than one week 
and spread out in a layer sufficiently thin to cause immediate drying. 
If it must be kept on the premises for longer periods it should be stored 
in fly-tight bins or composted in neat, clean-edged piles. 



62 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION 

Dead animals should be incinerated or if buried the carcasses 
should be liberally sprinkled with lime or crude oil and the ground 
well tamped. 

Flies are best poisoned inside the house by sweetened 2 per cent 
solutions of formaldehyde mixed with milk and exposed in saucers 
at night ready for flies early in the morning, other sources of water 
having been removed. 

The larvae may be destroyed in manure by sprinkling the pile 
with borax at the rate of % pound to 10 cubic feet of manure and 
following this application with enough water to carry the borax at 
least six inches into the mass. Repeated borax treatment will make 
such manure injurious to plants if used as a fertilizer. 

Mosquitoes. — These insects should be attacked in their breeding 
places, standing water, all accumulations of which should be drained 
or the depressions filled. If this is not practicable, oiling the surface 
with an oil made of equal parts of crude oil and kerosene will tem- 
porarily reduce the nuisance but must be repeated at intervals of two 
to three weeks. Inasmuch as certain mosquitoes are able to transmit 
malaria from one person to another care should be taken to prevent 
their entrance to living quarters by screening and individual capture 
if they succeed in gaining entrance. The malaria-transmitting species 
may be detected by their habit of standing with the head pointing 
down and the abdomen raised when at rest. 

Silver Fish Moth. — This wingless leaden colored insect sometimes 
becomes important through its eating starchy materials such as 
laundered sheets, bookbindings, wall paper, etc. They are controlled 
by use of a bait composed of 10 parts of starch to 1 part of white 
arsenic. 

Sow Bugs. — These crustaceans migrate indoors at the beginning 
of each rainy season. Damp cloths placed under a board at night 
outside the buildings or in basements collect large numbers which 
may be destroyed by soaking the cloth with hot water, kerosene or 
gasoline. 

(See also Poison Baits, Formulas 4 and 5, p. 72.) Sliced potatoes 
or carrots sprinkled with Paris green or white arsenic often give good 
control if placed where the sow bugs are numerous. 

Tule Bugs or Stink Bugs. — These bugs cause great annoyance by 
entering houses often in great numbers in search of shelter in the 
autumn time when they are driven by the rains from the lowlands 
where they breed and feed on other insects along the river margins 
and in moist places. Once in the house they are hard to get rid 



CIRCULAR 265] PLANT DISEASE AND PEST CONTROL 63 

of especially if the house is moist, but a well-warmed and dry house 
does not serve them well. Keeping doors and windows well screened 
and all cracks closed, particularly when lights are burning will help 
considerably in keeping them out when they are making their nights. 
The invasions are only temporary. 

CATTLE 

Ear Ticks — Ornithodorus megnini Duges — This tick lives its entire 
life within the auditory canals of the ears of domesticated animals, par- 
ticularly cattle, except when it leaves to deposit its eggs in the ground. 
The young ticks hatching from these eggs crawl on the bodies of avail- 
able animals and enter the ears. Control must be by individual treat- 
ment. The application of a half-and-half mixture of cottonseed oil 
and pine tar in quantity sufficient to fill the auditory canal is very 
effective. 

Horn Flies Haematobia serrata R. D. — These flies, about one-half 
the size of the common house fly cluster about the rump and head of 
cows, sucking blood and constituting a serious nuisance in the case of 
dairy cattle. They deposit their eggs on the freshly deposited cow 
manure. The young maggots live in this material until ready to 
change to an adult fly, when they burrow into the surrounding earth 
to pupate. The life history lasts from 10 to 16 days. 

Corrals should be cleaned of manure weekly or dragged with 
a heavy brush drag daily to break up the clots of manure and thus 
dry them out. 

Biting Lice, Trichodectes scalaris Nitzsch. — The biting louse may 
be differentiated from the sucking louse by its round head and the 
fact that it is never found with its mouth parts imbedded in the 
animal's flesh. It may be controlled by one dusting with sodium 
fluoride (commercial) mixed with flour in even proportions, or by 
dipping, spraying, or bathing with a coal tar dip (Formula 266) at 
intervals of ten days. 

Sucking Lice. — These lice suck the blood of the animals and may 
be distinguished from the biting lice by their pointed heads and the 
fact that they are generally found with their mouth parts plunged 
into the animal's flesh. Sodium fluoride, so successful for the biting 
lice, is useless against this class of lice. Coal tar dips applied as a dip 
or spray or rubbed on are effective but must be repeated at the expira- 
tion of ten days to be successful. Raw linseed oil applied with a brush 
at intervals of a week will also control both types of lice. 



64 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 

Lungworms, Dictyocaulus viviparus Bloch. — These worms are 
parasitic in the air passages of the lungs. The eggs containing living 
young are coughed up and swallowed, hatch out in the small intestine, 
and, after spending a period outside the body are taken in again with 
food or water, and after penetrating the small intestine are borne 
back to the lungs. They cause serious damage by causing a collapse 
of those portions of the lung from which the air supply is shut off 
by the blocking of the bronchioles, thus forming a favorable medium 
for the growth of pathogenic organisms that may actually cause the 
death of the infected animals. Chloroform injected into the nostrils 
in quantities sufficient to make the animals slightly groggy, often kills 
large numbers of the lungworms and greatly facilitates recovery. 
(See "Sheep" regarding the danger of chloroform treatment with 
this animal.) Sufficient food and proper shelter are very important. 
Infection is incurred in moist, swampy localities. Wherever possible 
such areas should be eliminated from the range or fenced off and 
drinking water supplied in troughs high enough to avoid contam- 
ination with feces. 

Ticks. — Various ticks attack the bodies of cattle. Where these 
occur in large numbers or where the tick concerned is the Texas 
Fever Tick, Margaropus annulatus Say, which may be recognized by 
its chestnut-colored shield and the fact that its first pair of legs 
originates on the "shoulders" and not close to the shield, measures 
should be taken for control. Dipping in an arsenical dip (Formula 
3a) is most satisfactory. Where only a few animals are concerned, 
spraying may be substituted for the dipping. 

Warbles, Hypoderma lineata de Villers. — These maggots which 
cause the lumps or swellings on the backs of cattle are the larvae 
of a fly resembling a bee which deposits its eggs on the heels or legs 
of cattle. On hatching these maggots bore into the skin and penetrate 
to their position on the back beneath the skin. When about ready to 
change to a fly a hole appears above the maggot which is used for its 
exit. It then falls to the ground, burrows into the earth for two or 
three inches whence it emerges in about three weeks as a full-grown fly 
ready to deposit eggs on other cattle. The control is individual in that 
the maggot when "ripe" must be forced out of the lumps on the back 
and destroyed. Care should be taken not to crush the warble in the 
wound for such accidents sometimes produce serious poisoning. If 
this happens the wound should be carefully washed out with water to 
which salt at the rate of two teaspoonfuls to the pint has been added. 



Circular 265] PLANT DISEASE AND PEST CONTROL 65 



SHEEP 

, Head Maggot, Oestrus ovis Linn. — These pests are the larvae of 
flies that deposit their eggs on living young near the nostrils. The 
young migrate up the nasal cavity penetrating to the sinuses where 
they are often trapped by their growth in size. Their presence may 
be detected by the attitude of the infected animal, which stands head 
down and inclined to one side and at intervals follows the inclination 
of its head around in circles. This may be distinguished from ' ' gid ' ' 
by the fact that with head maggot infestations there is a discharge 
from the nostrils. Some relief may be had by causing the animals to 
sniff up red pepper, the larvae being discharged by violent sneezing. 
Prevention is accomplished by the use of "salt logs" made by boring 
2 to 3 inch holes in a log, filling the cavities with salt and smearing the 
circumference of the holes with soft tar. The animals in attempting 
to get the salt keep their muzzles painted with tar which acts as a 
repellent. 

Lungworms, Dictyocaulus filaria Rud. — See "Cattle" for general 
consideration. Little can be clone in the way of treatment for sheep 
affected with lungworms as they are very susceptible to chloroform, 
which consequently cannot be used for these animals. Good food and 
comfortable shelter will generally accomplish the desired end although 
the sanitary precautions should not be overlooked. 

Scab. — This disease which manifests its presence by the ' ' tagging ' ' 
of the wool and crusting of the underlying skin is caused by a micro- 
scopic mite, Psoroptes communis var. ovis. Hering. These mites punc- 
ture the skin causing an intense itching; the roughening of the skin 
and eventually a crustiness causes the wool to fall out or ' ' tag. ' ' Con- 
trol is by means of dipping in lime-sulfur dip (Formula 17a). Pastures 
which have been used for infested sheep should not be utilized for 
clean sheep for three months unless drenching rains have intervened. 

Wool Maggots. — These pests are the larvae of flesh flies that, 
attracted by the odor of soiled wool, attack first the wool and later 
the flesh of the sheep. The points of attack are largely confined to 
the area about the hind quarters where the wool becomes soiled with 
feces. "Crutching, " the clipping of the wool around the anus and 
inside the hind legs, helps prevent infestation. Infested flesh should 
be cleaned of maggots by the application of sheep dip and the odor 
of putrefaction destroyed by formaldehyde or pine tar in order to 
prevent further infestation. "Jetting" of the hind quarters under 
100 pounds pressure with sheep dip to which 5 pounds of white 



66 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION 

arsenic has been added is curative and acts as a protection for from 
one to three months. The bodies of dead animals, in which these 
flies also develop in enormous numbers, should be incinerated. 

DOGS 

Fleas. — See " Household Insects." 

Mange or Scabies. — See "Sheep" for general consideration. 
Sarcoptes scabiei var. canis Linn. Treatment. — Affected parts should 
be thoroughly washed with warm water and soap until the skin is thor- 
oughly softened. Sulfur ointment made by mixing sulfur and lard 
should be carefully rubbed into the skin. This should be repeated 
every five days. 

Demodectic or Follicular Mange is commonly called the "Red 
Mange" of dogs. It is caused by a microscopic elongated mite known 
as Demodex folliculorum Simon which burrows into the hair follicles. 
The chances of cure are slight and valuable or valued dogs should 
be placed under the care of a skilled veterinarian where facilities 
are available for the production of auto-vaccines. Itchthyol (10 per 
cent) and formalin (5 per cent) are both highly recommended. 

Roundworms, Toxascaris limbata R. & H. and Belascaris mar- 
ginata Rud. — These worms normally inhabit the small intestine but 
are great wanderers and are often found in the stomach which accounts 
for their name of "maw" worms. The eggs are ingested with food 
contaminated by the feces of infested dogs. These hatch in the 
stomach and the larvae penetrate to the lungs, into the air spaces of 
the latter, up the windpipe and down the esophagus to their final 
resting place in the small intestine. This migration is often the 
cause of serious pneumonic difficulties in puppies. 

Control is by administration of oil of chenopodium at the rate of 
1 c.c. for each pound of body weight combined with a dose of castor oil. 

Tapeworms. — All tapeworms of the dog have an intermediary host, 
i.e. another animal in which the tapeworm lives and which must be 
eaten by the dog in order to infect the latter. The various tapeworms 
of dogs find their intermediary hosts in lice, fleas, rabbits, and sheep 
among others. The commonest tapeworm of dogs is Dipylidium cani- 
num Linn., the double pored tapeworm. 

Biting lice or larval fleas become infected with the larval stage 
of this parasite by eating particles of the dogs feces containing the 
"eggs" of this worm. The young form develops in the louse or 
flea and when these are eaten by the dog the larval tapeworm avoids 



Circular 265] PLANT DISEASE AND PEST CONTROL 67 

digestion, attaches itself to the lining of the intestine and becomes a 
mature tapeworm. The most efficient treatment is arecoline hydro- 
bromide in y 8 - to i/4-grain doses placed on the tongue of the animal. 
With valuable dogs or toy dogs this treatment should be administered 
by a veterinarian who would be able to recognize symptoms of poison- 
ing and apply the necessary antidotes. No preparation is necessary 
and the tapeworms are generally eliminated in from ten to fifteen 
minutes. 

SWINE 

Lice, Haematopinas suis Linn. — The control of the sucking lice of 
hogs is extremely important. The irritation together with the loss of 
blood occasioned by their attacks is the cause of considerable losses 
when taken in the aggregate. Crude oil is the best remedy. This 
may be applied by soaking it on burlap-wound posts in the corrals 
against which the hogs will rub, or by applying it to the surface 
of their wallows if the latter are located in the shade. 

Scabies or Mange, Common, see " Sheep. " — Demodectic, see 
"Dogs." 

The control of demodectic mange on hogs is seldom of economic 
importance, as the disease affects only the skin and is seldom serious 
during the relatively short life of the breeding stock. The same 
measures may be taken as for dogs. The snout and face about the 
eyes are the parts generally affected. 

Roundworms, Ascaris lumbricoides Linn. — For life history see 
"Dogs." 

Treatment — Starve the infested animals for twenty-four hours. 
Administer individually 4 c.c. of oil of chenopodium and 1 ounce of 
castor oil to each hog of less than 100 pounds and twice the dose 
for those over this weight. 

GROUND SQUIRRELS 

The five most effective methods of destroying ground squirrels are : 
(1) poisoning with strychnine; (2) fumigation with carbon bisul- 
phid (3) trapping; (4) shooting; (5) encouragement of the natural 
enemies of the ground squirrel. (See Circ. 181.) 

1. Carbon bisulphid is most effective when the soil is damp. 
When the ground is dry the gas escapes through the cracks in the 
ground. 



68 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 

2. Strychnine-coated barley is best used during the dry season 
because at this time the squirrels gather and store grain and hence 
are easily poisoned through their cheek pouches when in the act of 
carrying the poisoned grain. Rain and heavy fogs tend to wash the 
strychnine off the poisoned grain. 

3. Trapping and shooting are effective at any time, but are from 
six to twelve times more so before the young are out, before April 1, 
than later in the season. 

4. Powdered strychnine (sulfate) in fresh vegetables and fruit 
is especially effective in the dry season when green food is scarce. 
(Formula 33.) 

5. Red-tailed hawks, Golden eagles, badgers, weasels, and other 
natural enemies of the ground squirrel will prove valuable allies in 
the war on ground squirrels if they are only allowed to live. It costs 
little to let them alone to go about their business in the natural way. 

GOPHERS 

The five most effective methods of destroying gophers are: (1) 
poisoning with strychnine ; (2) trapping; (3) flooding; (4) fumigation 
with carbon bisulphid; (5) for permanent relief, the encouragement 
and protection of the gopher 's natural enemies, especially the barn owl 
and the gopher snake. 

The solution of the gopher problem lies in a combination of two 
or more of the above methods, rather than in any one of them. 
Where a large acreage is to be treated, poisoning with strychnine 
(Formula 34) will be found most effective in reducing the pest. Traps 
are safe, can be used at any time, and are effective in the hands of a 
man who is not afraid to dig and who uses care in setting and placing 
them. Trapping is especially adapted to pastures, where there might 
be danger of poisoning stock, and to gardens, orchards, and the banks 
of irrigation ditches. Carbon bisulphid should be used only when 
the ground is wet. Both traps and carbon bisulphid are good 
"follow-up" methods in getting the gophers which refuse to take 
poisoned bait. Land that can be successfully flooded, so as to drown 
out the gophers, has usually been graded for irrigation crops such as 
alfalfa. Flooding (irrigation) is therefore automatic, and it is com- 
paratively easy to hunt and kill gophers which are being flooded out. 
A man that kills all gopher snakes and barn owls on his place will 
have to fight gophers, and deservedly so. (See Bull. No. 340.) 



Circular 265] PLANT DISEASE AND PEST CONTROL 69 



RABBITS 

If very abundant, must be fenced out of young orchards and gar- 
dens to avoid serious damage. Shooting and poisoning are the prin- 
cipal means of destruction. An application of whitewash containing 
bitter aloes to the trunks of young trees is sometimes recommended, 
but this has not shown much value in actual practice. 

Soaked, chopped alfalfa sprinkled with strychnine, Paris green or 
white arsenic is very effective in destroying cotton-tails. 



RATS 

These pests should be handled by trapping if possible. Spring 
traps should be used, baited with fried bacon and the entire trap 
flamed with a burning newspaper before setting. When traps fail, a 
poison bait made by mixing barium carbonate with bananas, ham- 
burger steak, or moistened bran mash in the proportion of 1 part of 
poison to 4 parts of the carrier may be used. 



VENOMOUS INSECTS, SPIDERS, ETC. 

Among the few venomous insects, spiders, etc., the most noteworthy 
are the so-called kissing bugs (cone noses), hour glass or shoe button 
spider, the pajaroello tick and the scorpion. Two species of kissing 
bugs (Triatoma protracta Uhler, a black species, also known as the 
China bed bug or cross bug, and Rasahus thoracicus Stal, the two- 
spotted corsair, a reddish-brown species with a large brick red spot 
on each wing cover) inflict particularly painful bites which in turn 
may result in more or less severe symptoms such as vomiting and rash. 

These insects usually bite at night, but may also do so when 
disturbed during the day. Bathing the wound immediately with a 
1 to 1000 solution of mercuric chloride (poison) or strong ammonia 
will afford some relief. The same treatment may be applied for the 
sting of scorpions. 

The bite of the shoe button spider (Latrodectes mactans Fabr.) 
and that of the pajaroello tick (Omithodorus coreaceus Koch) may 
prove serious, and a physician should be consulted. The immediate 
application of potassium permanganate is recommended. 



70 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 

FORMULAS AND DESCRIPTIONS OF MATERIAL* 

ARSENICALS 

Acid Lead Arsenate (Lead Hydrogen Arsenate, Di-lead Arsenate, 
Often Labeled "Standard" or Lead Arsenate). — The acid type of lead 
arsenate contains more poison per pound than the basic type, is a 
stronger poison and acts more quickly. It is, however, somewhat sus- 
ceptible to the action of other chemicals, particularly those of an alka- 
line nature (such as soaps, lime-sulfur solution, etc.), and is more or 
less dissolved by them when used as a combination spray. In moist 
climates along the coast, or in continuous damp, cloudy weather else- 
where, whether used alone or in combination with other sprays, some 
of the arsenic is apt to be dissolved and to cause serious foliage injury. 
It is not considered a safe arsenical for use on stone fruits, beans, or 
other susceptible plants. 

Basic Lead Arsenate (Usually Labeled "Tri-plumbic" or " Neu- 
tral"). — The basic type of lead arsenate is a weaker poison and acts 
more slowly. It is not decomposed, however, by chemicals of an alka- 
line nature, such as are usually applied with it as a combination spray, 
nor by the damp weather of the coast regions. It is considered the 
only safe arsenical to use on stona fruits, beans, or other susceptible 
plants. 

The lead arsenates are usually sold as a paste containing about 
50 per cent of water, or as a dry powder. The paste should be thinned 
somewhat with water and worked into a smooth cream before adding to 
the spray tank. The powder may be added directly to the tank and 
mixed by means of the agitator. 

For codling moth and most defoliating insects use : 

Formula 1 

Dry acid lead arsenate (paste, 4 to 8 pounds) 2 to 4 pounds 

Water 100 gallons 

Or Formula 2 

Dry basic lead arsenate (paste, 5 to 10 pounds) 2% to 5 pounds 

Water 100 gallons 

Dry or powdered lead arsenate contains twice as much arsenic as 
the paste; therefore use only one-half as much of it. 

* Mr. Geo. P. Gray furnished much of the information relative to the 
chemical compositions and reactions of these insecticides. 



Circular 265] PLANT DISEASE AND PEST CONTROL 71 

Zinc Arsenite is a stronger and more active poison than either type 
of lead arsenate, and is useful in controlling the various caterpillars 
which are troublesome on pears and apples in the early spring, but is 
very apt to cause injury if the application is made after the time of 
full bloom. 

Formula 3 

Zinc arsenite powder 3 pounds 

Water 100 gallons 

White arsenic (Arsenic trioxide) is only sparingly soluble in 
water, although sufficiently so to prohibit its use on plants as an 
insecticide. Its use as a stomach poison is therefore limited to the 
preparation of poison baits for the control of grasshoppers, army- 
worms, cutworms, etc., and to some other cases where the insecticide 
is not to be applied to growing plants. 

Formula 3a 

Government Arsenical Dip. 

Caustic soda 4 pounds 

White arsenic 8 pounds 

Sal soda crystals 8 pounds 

Pine tar 1 gallon 

Water to make 500 gallons 



Dissolve the caustic soda in an iron vessel (zinc, tin or solder 
will be corroded) using 1 gallon of water. Then add the arsenic 
slowly, with constant stirring. The temperature of the solution while 
mixing should be just below boiling. Add the sal soda after the 
arsenic is dissolved, stir, then make up to 5 gallons. 

Emulsify the pine tar by dissolving % of a pound of caustic soda 
or concentrated lye in 1 quart of water and adding to this 1 gallon 
of pine tar. Stir until a clear molasses-like liquid results. If a 
drop of this does not mix perfectly with water, stir in caustic soda 
until a perfect mixture of tar and water results. 

To prepare the dip, dilute the emulsified tar with two or three 
times its volume of water and pour this into the dipping tank, after 
the latter is three-fourths full. Add the arsenical solution in the 
same way and make up to the desired amount. 

This solution is very poisonous and should be handled and disposed 
of with great care. 



72 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 

Poison Bran Mash. 

Formula 4 

Bran 25 pounds 

White arsenic 1 pound 

Molasses (cheap blackstrap preferred) 2 quarts 

Mix the arsenic and the bran dry and add the molasses which has 
been diluted with water. Add enough water and mix thoroughly to 
make a dry mash which will broadcast easily. 

Citrus Bran Mash. 

Formula 5 

White arsenic 1 pound 

Molasses (cheap blackstrap preferred) 2 quarts 

Lemons (or oranges) 6 fruits 

Water (about) 4 gallons 

Bran 25 pounds 

Mix the above materials as follows: Stir thoroughly the white 
arsenic, molasses, and water first. Grind the lemons, including the 
rinds, in a meat grinder, or chop fine, and add to this liquid. Then 
slowly pour this over the bran and stir thoroughly until an even mix- 
ture is secured. 

The amount of water to use in the preparation of these baits will 
vary according to the coarseness of the bran or substitutes. A barely 
moist mash is preferable to a wet one because it does not harden under 
the heat of the sun and remains palatable, while wet mash becomes 
baked and unattractive. 

Substitutes in Poison Baits. — Paris green may be substituted for 
white arsenic in Formulas 4 and 5. Alfalfa meal, shorts, or rice meal 
have been successfully used as a substitute for bran in the preparation 
of the above formulas. 

Sodium Arsenite. — This arsenical is readily soluble in water and 
is one of the most violent of the plant poisons. It probably acts more 
quickly than any of the better-known arsenical poisons, and is com- 
monly used in the preparation of weed killers, poison fly-papers, cattle 
dips for the control of ticks, ant syrups, and to some extent in the 
preparation of poison baits. 



Circular 265] PLANT DISEASE AND PEST CONTROL 73 

Sodium arsenite may be purchased ready made as a white powder, 
but it is not always readily obtained at pharmacies, nor can it always 
be depended upon to contain a uniform amount of arsenic. This 
chemical may be easily prepared from white arsenic by combining the 
latter in the presence of water with sal soda, soda ash, caustic soda, 
or a good grade of concentrated lye in the following proportions : 

Sal soda or washing soda, 2 parts to 1 part of white arsenic. 
Soda ash, 1 part to 1 part of white arsenic. 
Caustic soda, 1 part to 2 parts of white arsenic. 
Concentrated lye, 1 part to 2 parts of white arsenic. 

If sal soda or soda ash is used it is necessary to boil the mixture 
fifteen or twenty minutes before the arsenic is dissolved. If caustic 
soda or concentrated lye is used, little or no heat is necessary. In 
either case, a corrosive chemical known as sodium arsenite is formed. 

A soluble arsenical can be made by using 1 part of caustic soda 
to 4 parts of white arsenic (arsenic AS 2 3 ) trioxide, such a solution, 
however, has a tendency to form crystals on standing. 

Sodium Arsenite. 

Formula 6 

Sal soda 2 ounces (or 2 pounds) 

White arsenic 1 ounce (or 1 pound) 

Water (about) y 2 pint (or 1 gallon) 

Put all the ingredients together in an iron or graniteware kettle 
(do not use aluminum) of sufficient size to allow for considerable 
frothing, and boil fifteen or twenty minutes, or until the solution is 
clear. 

Ant Syrups. 

Formula 7 

Strong for Weak for Argentine ants 

native ants Large quantity Small quantity 

White arsenic 2 oz. 1 oz. 1 scruple 

Concentrated lye 1 oz. 1 oz. y 2 teaspoonful 

Sugar 1 lb. 20 lbs. 1 lb. 

Water 1 pt. 3 gals. 1 pt. 

The U. S. Bureau of Entomology recommends a later formula for 
the preparation of Argentine ant syrup which is said to be superior 
to any other formula tested by them, "on account of its stability at 
high temperatures, freedom from crystalization, and continued attrac- 
tiveness. ' ' 



74 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 

Government Argentine Ant Syrup. 

Formula 8 

Granulated sugar 12 pounds 

Water 11 pints 

Tartaric acid (crystalized) 7 grams 

Benzoate of soda 9 grams 

Boil slowly for 30 minutes. Allow to cool. 

Dissolve sodium arsenite (C. P.) % ounce 

In hot water y 2 pint 

Cool. Add poison solution to syrup and stir well. 

Add to the poisoned syrup : 
Honey, strained 2 pounds 

Mix thoroughly. 



COPPER COMPOUNDS 

Bordeaux Mixture (Average Strength). 

Formula 9 

Bluestone 16 pounds 

Quicklime 20 pounds 

Water 200 gallons 

Dissolve the bluestone and slake the lime in separate vats, the blue- 
stone to be kept from contact with all metals except copper. Thor- 
oughly mix the dissolved bluestone with one-half the water and the 
slaked lime with the other half. Run the two mixtures together in a 
single stream into the spray tank through a fine screen. For conven- 
ience, the mixing vats may be placed on an elevated platform, and the 
two parts mixed as they are flowing into the spray tank. The milk of 
lime should be continuously stirred during the mixing. 

A somewhat less satisfactory Bordeaux mixture may be made as 
follows : Slake the lime and dissolve the bluestone in separate barrels 
as above. Fill the spray tank half full of water; add the dissolved 
bluestone ; strain in the slaked lime while the agitator is running ; add 
remainder of water, and mix thoroughly. 



Bordeaux Paste. 

Formula 10 

A. Bluestone 12 pounds 

Water 8 gallons 

B. Quicklime 24 pounds 

Water 8 gallons 

Dissolve the bluestone and slake the lime separately in the amounts 
of water specified. Then mix together equal quantities of each ingre- 
dient, making up only enough for each day's use. 



Circular 265] PLANT DISEASE AND PEST CONTROL 75 

Commercial Bordeaux Mixture. — Several preparations of this sort 
are on the market in the form of a paste or dry powder to be diluted 
with water. Objection is sometimes made to these preparations that 
they will not remain in suspension in water as well as the home-made 
Bordeaux mixture, but some of them are probably as good or better 
than the average mixture prepared on the ranch. The commercial 
preparations are more expensive, but also more convenient for use, 
and are of especial value to the small grower. 

Resin-Bordeaux Mixture. 

Formula 10a 

Bluestone _ 20 pounds 

Lime 26 pounds 

Resin 10 pounds 

Soap (soft) 16 pounds 

Water 200 gallons 

Melt the resin in an iron pot ; then add the soft soap, heat and stir 
until well mixed and quite soft. Add hot water and boil and stir for 
some time until thoroughly dissolved. Add this to the Bordeaux 
which has been made in the usual way. (From Univ. Calif. Exp. 
Sta. Bull. 165, p. 77.) This is for use on plants with very smooth 
waxy surfaces on which fungicides do not spread and adhere well. 

Bluestone (Copper Sulfate). — A soluble compound of copper, the 
raw material for the preparation of most other compounds of copper. 
This cannot be used on foliage. 

For dipping grain use : 

Formula 11 

Bluestone 1 pound 

Water 5 gallons 

Dip for 3 minutes. 

Followed by: 

Quicklime 1 pound 

Slaked in water 10 gallons 

For lemon wash water use: 

Formula 12 

Bluestone 1% pounds 

Water 1000 gallons 

Copper Carbonate. — For dust treatment of grain, use Formula 
11a. For dusting wheat for bunt, use 2 ounces of copper carbonate 
dust to a bushel. The dust should be intimately mixed to thoroughly 



76 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 

cover each seed. The copper corbonate dust should contain 50 per 
cent of copper in the form of carbonate and hydrate of copper, and 
should be sufficiently fine to weigh approximately 32 pounds to a 
cubic foot. The dusted seed may be stored without injury from the 
dust. 

Ammoniacal solution of copper carbonate. — This solution contains 
no sediment and on drying leaves no unsightly marks. It may there- 
fore be used when the spotting that the Bordeaux mixture causes 
precludes the use of that fungicide. The mixture consists of a solution 
made by dissolving copper carbonate in ammonia-water in the follow- 
ing proportions: 

Copper carbonate 6 oz. 

Ammonia, about 3 pints 

Water 50 gals. 

Weigh out the proper amount of copper carbonate. Set a very 
small portion of this aside and dissolve the remainder of it in diluted 
ammonia (dilute ammonia with water to about 5 times its volume), 
using only enough ammonia to dissolve it. Then add the portion of 
copper carbonate which was reserved. This will insure the use of no 
more ammonia than is necessary. It is better to have a little too 
much of the carbonate in the solution than to have too much ammonia. 
The strong solution made in this way may be diluted with the proper 
amount of water. The copper carbonate may be purchased directly 
from the drug store, or it may be prepared at home. 

SULFUR AND SULFUR COMPOUNDS 

Dry Sulfur. — For dusting upon plants for the control of surface 
mildew, red spider, or other parasites, the fineness of the sulfur is an 
all-important consideration. Flowers of sulfur, the finest and fluffiest 
grade of sublimed sulfur, has been heretofore recommended for appli- 
cation as a dust, but at present there are upon the market several 
brands of extremely finely ground sulfurs, which are as fine as some 
of the best grades of sublimed sulfur and no more expensive. Some 
of these sulfurs, which have been specially prepared for dusting, are 
ground to pass a 200-mesh bolting cloth. These are apt to cake and 
to clog the dusting apparatus. If 9 parts of sulfur are thoroughly 
mixed with 1 part of hydrated lime, kaolin, or other inert powder, 
these difficulties may be avoided. 



Circular 265] PLANT DISEASE AND PEST CONTROL 77 

Sulfur Pastes or Wettable Sulfurs. — For various reasons it is often 
desirable to mix sulfur and water and apply it to plants as a spray. 
Sulfur, however, is not easily wetted with water and it is a difficult 
matter to make a uniform mixture of the two. It has been found that 
a number of substances — soap, calcium casemate, oleic acid, glue, 
diatomaceous earth, flour, dextrin, etc. — when mixed with water and 
sulfur have the property of counteracting the mutual repulsion of 
sulfur and water without otherwise altering the nature of the sulfur. 
Certain of these substances have been used in the preparation of 
commercial sulfur pastes or wettable sulfurs. These commercial 
pastes, as now manufactured, contain from 45 to 50 or more per 
cent of sulfur in a very finely divided condition, the remainder being 
water and one of the substances mentioned above. The effect of these 
pastes is that of dry sulfur. The usual strength to use is : 

Formula 13 

Commercial sulfur paste 8 to 21 pounds 

Water 100 gallons 

Home-Made Wettable Sulfur. — A satisfactory wettable sulfur can 
be easily made at home by the use of glue water as follows : 

Formula 14 

Powdered glue % ounce 

Hot water iy 2 gallons 

Sulfur (flowers or powdered) 5 pounds 

Water to make 100 gallons 

Dissolve the glue in hot water or soak over night in iy 2 gallons 
of cold water. Add the glue water to the sulfur a little at a time 
and work up into a smooth paste as free from lumps as possible. 
Rubbing is better than stirring. Wash this paste into the spray tank 
through a fine screen, using the remainder of the glue water to wash 
it through and a stiff brush to break up the remainder of the lumps. 
Then add plain water to make 100 gallons. 

Another formula more expensive than the above is : 

Formula 15 
Make a paste of: 

Flour 4 pounds 

Water 4 gallons 

Mix this with: 

Sulfur (sublimed or powdered) 5 pounds 

Then add : 

Water to make 100 gallons 



78 university of california — experiment station 

Formula 15a 

Self-Boiled Lime-Sulfur Wash. — A preparation of sulfur largely 
used in the eastern states for a summer spray on peach and other 
tender foliage and comparable in use with the wettable sulphur 
preparations. 

Quicklime 32 pounds 

Sulfur 32 pounds 

Water to make 200 gallons 

Put the quicklime in a suitable container and add water to start 
slaking, about 12 gallons (hot water for sluggish lime and cold for 
active.) Work the sulfur through a sieve and add to the lime with 
stirring to prevent caking. Add enough water to make a paste. 
When the violent boiling ceases, add cold water to make up to the 
final amount. If allowed to stand hot, the mixture becomes caustic. 
The wash must be strained and applied with a pump having a good 
agitator. 

The usual grades of sublimed or powdered sulfur may be wetted 
in the manner described in Formulas 14 and 15, but for the best 
results the finest grade of sulfur obtainable should be used. The 
sulfurs especially prepared for dusting are recommended for this 
purpose. 

Lime-Sulfur Solution.-^This is the most active form in which 
sulfur compounds are commonly used in the control of insects or 
fungi. Its causticity prohibits its use on any foliage except that of the 
more hardy plants, and then in a very dilute form. Its principal 
use is as a dormant spray for the control of certain fungus diseases, 
scale insects, red spider, and a variety of other pests of deciduous 
trees. 

Commercial Lime-Sulfur Solution. — The horticulturists of the 
state are being supplied with concentrated commercial lime-sulfur 
solution of good quality and at reasonable prices. The great bulk 
of this important pest remedy used in the state is therefore of com- 
mercial manufacture, testing between 32° and 34° Baume. It is only 
necessary to dilute this with water before spraying. 

Home-Made Lime-Sulfur Solution. 

Formula 17 

Stone lime 50 pounds 

Sulfur (sublimed or powdered) 100 pounds 

Water to make 50 gallons 



Circular 265] PLANT DISEASE AND PEST CONTROL 79 

Heat about one-third of the total volume of water required. When 
the water is hot add all of the lime, and then immediately all the 
sulfur, which should previously have been made into a thick paste with 
water. After the lime is slaked another third of the water should 
be added, preferably hot, and the cooking should be continued until 
a clear orange-colored solution is obtained (usually 45 to 60 minutes), 
when the remainder of the water should be added, either hot or cold, 
as is most convenient. The boiling due to the slaking of the lime 
thoroughly mixes the ingredients at the start, but subsequent stirring 
is necessary if the wash is cooked by direct heat in a kettle. After 
the wash has been prepared it must be allowed to settle and then 
strained through a fine sieve as it is being run into the spray tank. 
The resultant product is a concentrated solution of lime-sulfur, which 
should be diluted about six times with water for a winter spray. 

Dry Lime-Sulfur. 

Lime-sulfur is now obtainable in the form of a dry powder which 
is used by dissolving in water. 40 pounds to 200 gallons of spray 
is usually recommended for application on dormant trees. A strength 
of about 10 pounds to 200 gallons is generally recommended for use 
on foliage as in treating apple scab, red spiders, etc. 

The recommendations for the dry lime-sulfur sprays call for 
the use of a smaller amount of total sulfur in general than is used 
with the liquid lime-sulfur solution, but the comparative efficiency 
of the preparations seems not to be fully determined. 

Formula 17a 
Lime-Sulfur Dip. 

Lime (unslaked) 8 pounds 

(or 11 pounds of commercial hydrated lime) 

Flowers of sulfur 24 pounds 

Water 100 gallons 

Slake the lime, sift in the sulfur and make a thin paste ; add 
water to make 30 gallons, and boil for one hour, stirring during the 
process. Add water while cooking to maintain the original amount 
of 30 gallons. Strain or siphon off the liquid and make up to 100 
gallons. An excess of lime or sediment in the dip will injure the 
sheep and wool. 

The standard lime-sulfur dip as made above may be combined 
with one-half standard arsenical dip (see Formula 3a) for sheep 
1 Hicks." 

Alkali Sulfides. — Sulfides of soda ("soluble sulfur") are some- 
times used in place of lime-sulfur solution and have some advantages 
over the liquid preparations. 



80 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION 



PDB or PARA-DICHLOROBENZENE, A NEW SOIL FUMIGANT 

The use of para-dichlorobenzene as a soil fumigant to control 
soil infesting insects has created a large interest in California. The 
experiments conducted during the past two years, while not exten- 
sive, will be of interest in outlining a larger practice for next season. 

The material in question is a white crystalline substance which 
is insoluble in water and evaporates slowly at a temperature of 55° 
to 75° F. and more rapidly at higher temperatures. The vapor is 
more than five times heavier than air and more than twice as heavy 
as carbon bisulfide vapor. It possesses a weak ether-like odor which 
is practically nonpoisonous and noncombustible. 

Common name of material. — Para-dichlorobenzene has such a long 
name that it seems advisable to abbreviate it by using P. D. B. for 
short. Various trade names such as "Paracide," " Crystal Glass," 
etc., are already appearing, and many others will soon follow. 

Conditions of application. — In applying the material two things 
are important ; soil moisture and temperature. Because gases do not 
readily circulate in a thoroughly wet soil it is useless to apply para- 
dichlorobenzene unless the soil is not more than ordinarily moist, 
as is usually the case in California during the summer and fall except 
just after irrigations. In such cases a week or two following the 
application of water would be preferable. The soil temperature 
should range from 75° to 85° F. for the best results, for under such 
conditions the para-dichlorobenzene volatilizes more rapidly and the 
insects are more active, requiring a greater air supply, and are con- 
sequently more readily killed by the vapor. 

Time of application. — In California the period from the first of 
May until November may be roughly designated as the proper time 
to make the applications, provided the soil temperature is over 55° F. 
and the soil moisture is not excessive. 

Methods of application. — From % to 1 ounce of para-dichloro- 
benzene is sufficient to treat an average size tree. First, level the 
surface of the soil around the base of the tree; then sprinkle the 
material around the tree in a contiuous band or circle two inches wide 
with the inner margin two to four inches from the bark of the tree. 
Cover the material with soil around the base of the tree to a depth 
of from two to four inches and pack well with several strokes of 
the shovel. 



Circular 265] PLANT DISEASE AND PEST CONTROL 81 

Kinds of trees to treat. — Under eastern conditions, where the use 
of this insecticide has been quite extensive, it has been applied chiefly 
to peach trees on peach root-stocks. The eastern investigators caution 
against using it on trees under six years of age, although younger trees 
are reported to have been treated with no injurious results in many 
instances. 

In California apricot trees on Myrobalan rootstock and infested 
with the peach tree borer have been treated with .good results in 
killing the borers without injury to the trees. 

Even nursery stock on Myrobalan and peach roots treated in the 
early summer showed no ill effects, but such work should receive 
more attention before general recommendations can be made. 

California conditions are so different from those in the southern 
and eastern states that it is to be expected that we shall encounter 
many unusual problems in the handling of the material and that its 
uses may be very greatly enlarged. The Division of Entomology 
and Parasitology is contemplating a large series of orchard demon- 
strations and experiments during the coming year in order to have 
as much local information as it is possible to accumulate in that 
time. 

Not for flat-headed borers. — Para-dichlorobenzene is being recom- 
mended by some insecticide dealers for all woodboring insects, par- 
ticularly for the flat-headed apple tree borer. This insect and the 
other wood borers which work above ground cannot be satisfactorily 
reached by the fumes of the fumigant and cannot be controlled by it! 

CRUDE PETROLEUM 

The use of crude petroleum is almost entirely limited to the winter 
spraying of deciduous trees when the buds are entirely dormant. It 
is generally applied from November to February. The crude oil emul- 
sion is especially recommended for black scale (Saissetia oleae), Euro- 
pean fruit Lecanium (Lecanium corni), European or Italian pear scale 
(Epididiaspis piricola), cherry scale (Lecanium cerasorum) , and other 
scales infesting deciduous fruit trees. It is practically the only spray 
treatment which has been effective against European or Italian 
pear scale, and will destroy the winter eggs of many of the aphids, of 
the red spider, and of some of the defoliating caterpillars. 

When crude oil is thoroughly applied it sometimes penetrates the 
fruit buds to a considerable extent, and may injure and even kill some 
of them. The great majority of the buds are not injured, however, 
but appear to be stimulated to a more vigorous growth, and to the 



82 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 

production of foliage resistant to disease. It is good practice, especi- 
ally in dry seasons, not to apply crude oil emulsion until there is 
indication of swelling of the buds. 

A natural crude petroleum, testing about 23° Baume, is preferred, 
as it contains some of the lighter and more penetrating oils. Heavier 
crude oils have given satisfactory results, even those testing 18° and 
even lower. Residiuum oils (the residue of crude petroleum after the 
lighter portions have been distilled off) can be used if natural crude 
oil is unobtainable, provided their content of asphaltum is not too high 
to prevent their emulsification. 

Crude Oil Emulsion. 

Formula 18 

Water to make 200 gallons 

Liquid soap 3 gallons 

Natural crude petroleum (21°-24° Baume) 25 gallons 

Partly fill the spray tank with water, add the liquid soap, agitate 
thoroughly for one minute, add crude oil and continue the agitation 
while running in the remainder of the water. If liquid soap cannot be 
obtained, use 20 pounds of fish oil soap dissolved in 10 gallons of boil- 
ing water to which 3 pounds of caustic soda or lye have been added. 
To kill moss or lichens on fruit trees, add 2 pounds of caustic soda 
or lye to the formula. 

During the spraying operation this emulsion should be thoroughly 
agitated and great care taken to wet all of the twigs. From 8 to 10 
gallons should be used on a tree. 

PETROLEUM DISTILLATES 

Kerosene, of about 40° Baume, applied in the form of an emulsion, 
has been used to a considerable extent as an insecticide, particularly 
on citrus trees. The cheaper, unrefined distillates have now largely 
replaced kerosene as a foliage spray. These are more effective as 
insecticides, so that smaller percentages may be used in the emulsions, 
but coupled with their superior insecticidal properties is their greater 
toxicity to fruit and foliage. The toxicity varies with climatic con- 
ditions, foliage injury being most certain in dry weather with a tem- 
perature of 95° F. or more. Unfortunately, the season when spraying 
is most effective against scale insects on citrus trees is often during 
the hottest and driest months. It seems impossible to guarantee im- 
munity from damage under all conditions with any of the distillates 
obtainable. 



Circular 265] PLANT DISEASE AND PEST CONTROL 83 

Little injury to citrus fruit and foliage occurs in the coast regions 
where distillate emulsions have been used, but in the interior sections 
the use of this insecticide is \ery hazardous. 

Spraying with distillates, or with any other material, is not recom- 
mended as a substitute for fumigation in commercial citrus orchards, 
except in the case of young orchards, trees about dooryards, or where 
fumigation may not be convenient, or infestation may be light or 
limited to occasional trees. In such cases, Formula 19 is considered 
the most satisfactory. 

Kerosene emulsion is the safest of the petroleum-distillate sprays, 
although the most expensive. The "W. W." or "Water White" is a 
trade name of a low-grade kerosene and is safer than the usual grade 
of material sold as "distillate." The highly refined "case goods" 
kerosene has been found to cause the least amount of injury of any of 
the petroleum derivatives, but its cost is prohibitive except on a small 
scale. If much of the kerosene emulsion is allowed to run down the 
trunks of young trees, injury is likely to occur just beneath the surface 
of the ground. 

The following formula is intended for use on citrus trees : 

Kerosene Emulsion. 

Formula 19 

Kerosene 15 gallons 

Liquid soap % gallon 

(Or hard soap 4 to 12 pounds) 

Water to make 200 gallons 

If liquid soap is available, it is preferable to hard soap, since it 
requires no heating. Hard soap, preferably fish oil soap, is cut in thin 
slices and dissolved in hot water. The soap is placed directly in the 
spray tank with 10 or 15 gallons of water or more (the exact amount 
is not important) and the engine then started. The oil is now added 
slowly, and the materials are emulsified by being run through the 
pump under pressure. After a few minutes the rest of the water may 
be added, and the spray is ready to be applied. 

Certain "tree" distillates, testing 31° to 32° Baume, said to be 
selected and partially refined, have lately displaced to a considerable 
extent the heavier distillates of 27° to 28° for use on citrus trees. 

"Tree" Distillate Emulsion. 

Formula 20 

Tree distillate (31°-32° Baume) 4 gallons 

Liquid soap % gallon 

(Or hard soap 4 to 12 pounds) 

Water to make 200 gallons 



84 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION 

These materials are emulsified in the manner explained for the 
kerosene emulsion, Formula 19. If the distillate is used without 
soap, the following is the formula: 

Straight "Tree" Distillate. 

Formula 21 

Tree distillate (31°-32° Baume) 4 to 6 gallons 

Caustic soda (95 per cent) 7 pounds 

Water to make 200 gallons 

In the case of the straight distillate, the oil is kept in suspension 
in the water by agitation and forms an unstable mechanical emulsion, 
which separates quickly on standing. In using this it is necessary to 
have the spray outfit equipped with a powerful and efficient agitator, 
which must be kept going continuously during the spraying operation. 

The use of petroleum-distillate sprays against black scale on olive 
trees is now being recognized as profitable. For this purpose the 
heavier distillates of 28° to 30° Baume, being more effective, are used, 
since olive foliage is very resistant to spray injury, and also because 
the spray can be applied through the winter months when low temper- 
atures and high humidities are the rule. 

Distillates of this density are also much used as a dormant spray 
on deciduous trees, although crude oil sprays are replacing distillates 
more and more for this purpose. 

Heavy Distillate Emulsions. — For use on olives, the following 
mechanical emulsion is recommended: 

Formula 22 

Distillate (28° Baume) 7 gallons 

Caustic soda (95 per cent) ...5 to 7 pounds 

Water to make 200 gallons 

First dissolve the caustic soda in a small amount of water and add 
to the water in the spray tank ; begin the agitation and slowly add the 
distillate, continuing the agitation during application. This spray 
will also remove lichens or moss from trees. 

If the amount of crude oil is reduced from 25 gallons to 15 gallons 
in Formula 18, the crude oil emulsion may be used on olive trees for 
the control of black scale. 

For use on dormant deciduous trees the following is recommended : 

Formula 23 

Distillate 27°-28° Baume) 20 gallons 

Fish oil soap 30 pounds 

Water to make 12 gallons 



Circular 265] PLANT DISEASE AND PEST CONTROL 85 

Dissolve the fish oil soap in water, heating it to the boiling point ; 
add the distillate, and agitate thoroughly while the solution is hot. 
For use, add 20 gallons of water to each gallon of the above mixture. 

Commercial Prepared Emulsions and Miscible Oils. — Many grow- 
ers realize the difficulty in securing proper materials for home-made 
emulsions and the variability of the home-made mixtures even under 
the best conditions. They prefer to buy manufactured products, 
especially when only small quantities are needed ; but the commercial 
emulsions and miscible oils are no more effective than a good home- 
made preparation and are only more convenient. These preparations 
are on the market in great variety, many being sold under trade 
names. Practically all grales of petroleum distillates, as well as crude 
petroleum, are obtainable in a form ready to be used, after simple 
dilution with water. If these ready-made preparations are to be 
used, it is especially important to purchase only from reliable and 
well-known manufacturers or dealers. The commercial products in 
general are satisfactory for use for the purposes indicated for the 
above formulas. 

The following is recommended for the control of thrips: 

Distillate Emulsion and Tobacco Extract. — Government formula. 

Formula 24 

The government formula for the control of pear thrips is the 
following : 

Distillate emulsion 10 gallons 

Nicotine sulfate 40 per cent 1 pint 

Water to make 200 gallons 

"When this formula was first prepared there were few commercial 
oil sprays on the market, so that it was necessary first to make a dis- 
tillate emulsion (Formula 23), In recent years there have appeared 
the miscible oils,* which may be used as follows: 

Formula 24a 

Miscible oil 5 gallons 

Nicotine sulfate 40 per cent 1 pint 

Water to make 200 gallons 

These formulas are for use against the adult ' ' black thrips, ' ' and 
should be applied liberally as soon as any considerable number of in- 
sects are found upon the trees. Do not fail to make daily inspections 
after the buds begin to swell. Applications should be repeated if 
necessary until the adults begin to lessen in numbers. 



86 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION 

In case the " white thrips" appear in destructive numbers later, 
the same formula may be safely used if the oil content is decreased 
and the nicotine increased as follows: 

Formula 24& 

Distillate emulsion 6 gallons 

Nicotine sulfate 40 per cent 1% pints 

Water to make 200 gallons 

Formula 24c 

Miscible oil 3 gallons 

Nicotine sulfate 40 per cent 1% pints 

Water to make 200 gallons 

For work with thrips, the greater force and volume delivery of the 
spray gun has rendered it superior to the spray rod, insuring not only 
a better but a quicker and easier job. The loss in material is more 
than overcome by the rapidity and ease of operation. 

The resin wash is chiefly used for young and tender nursery stock, 
because it does not cause the injury often following the application 
of petroleum distillates. The preparation is: 

Formula 25 

Resin 10 pounds 

Caustic soda (76 per cent to 95 per cent) 3 pounds 

Fish oil iy 2 pounds 

Water to make 50 gallons 

To a gallon of hot water in an iron kettle add the fish oil and the 
resin, and heat until the latter is softened. After first dissolving the 
caustic soda in a small quantity of water add it and stir the mixture 
thoroughly. After this pour in enough water to make 50 gallons of 
spray material. 

Crude Carbolic Acid Emulsion. — For citrus trees. 

Formula 26 

Fish oil soap 40 pounds 

Crude carbolic acid 5 gallons 

Water to make 40 gallons 

Dissolve the soap completely in hot water, add the carbolic acid 
and heat to the boiling point for twenty minutes (reserve some water 
to add in case the mixture begins to boil over.) For use, add 20 
gallons of water to every gallon of the above solution. The emulsion 
needs little or no agitation. 



Circular 265] PLANT DISEASE AND PEST CONTROL 87 

CRUDE CARBOLIC ACID AND DISTILLATE EMULSION 

Formula 26a 

Fish oil soap (or liquid soap, 5 gallons) 40 pounds 

Crude carbolic acid (25 per cent) 5 gallons 

Distillate 27°-28° Baume) 5 gallons 

Water to make 50 gallons 

Prepare as with Formula 26, adding the distillate after the crude 
carbolic acid. This mixture is specially recommended for mealybugs 
on dormant deciduous fruit trees. Dilute 1 to 20 for use. 

Formula 265 

Coal Tar Creosote Dip. — Coal tar derivatives which may be creosote 
oil, crude carbolic acid or cresylic acid emulsified by means of soap 
are also used. These are sold under various trade names and should 
be used according to directions. The requirement which has been 
made for such dips by the United States Department of Agriculture 
is that when diluted for use they shall contain "one per cent by 
weight of coal-tar oils and cresylic acid. In no case should the diluted 
dip contain more than four-tenths of one per cent nor less than one- 
tenth of one per cent of cresylic acid.'' 

These preparations cannot be used in very hard water except 
by a preliminary water softening. Hard water may be softened 
by dissolving lye at the rate of 12 ounces of high-grade concentrated 
lye to 100 gallons of water ; then add the dip. 

If the emulsion still breaks or forms in globules after treatment 
with lye it will be necessary to use lime-sulfur solution or an arsenical 
dip. 

TOBACCO PREPARATIONS 

Concentrated commercial preparations of tobacco have almost en- 
tirely superseded the home-made tobacco infusions on account of their 
greater convenience and uniformity. A material containing 40 per. 
cent nicotine in the form of nicotine sulfate is recommended for the 
preparation of contact insecticides containing nicotine. The usual 
formula is: 

Formula 27 

Tobacco extract (nicotine sulfate, 40 per cent 1 pint 

Fish oil soap , 4 to 5 pounds 

Water 100 to 150 gallons 

For small quantities, use 1 teaspoonful to 1 gallon of water. 



88 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 



Formula 27a 

Nicotine sulfate, 40 per cent 1 pint 

Dry billboard paste 2 pounds 

Water 150 gallons 

Make a paste of the dry material and add it to the water and nico- 
tine. This spray is intended for plants like potatoes, tomatoes, etc., 
which are sensitive to soap mixtures. 

Tobacco Dust. — Finely ground tobacco dust finds some use as an 
insecticide, particularly in the control of aphids. Fifty per cent of 
kaolin or hydrated lime is sometimes mixed with it as a diluent. 

NICODUST AND COMBINATIONS 

Nicodust, invented and named by Professor Ralph E. Smith, is 
composed of a carrying substance, like finely powdered kaolin or lime, 
treated with a concentrated solution of nicotine sulfate, commercially 
known as " Nicotine Sulfate 40 per cent." The nicotine in such com- 
bination, especially with lime, becomes very volatile and is quickly 
driven off by heat. In this form therefore it acts largely as a fumi- 
gant, but may be effective as a contact poison as well. As soon as 
mixed, the dust should be packed in air-tight containers to retain 
the nicotine content. The best results in killing insects have been 
secured when the temperature is over 70° F., and very poor results 
have followed its use in cold weather. The various strengths are 
usually denoted by the amount of "Nicotine Sulfate 40 per cent" 
contained, as follows: 2 per cent "Nicotine Sulfate 40 per cent," 
4 per cent, 5 per cent, 6 per cent, 10 per cent, etc. A statement of 
the actual amount of nicotine is more accurate and is required in 
the guarantee of commercial preparations. 

The name nicodust does not belong exclusively to any particular 
mixture or company, but was originated as a convenient name for all 
mixtures of this sort. 

Arsenate of lead and sulfur are mixed with nicodust at the time of 
manufacture and give convenient combinations for treating different 
types of insects or insects and fungus diseases at one application. 
Sulfur-nicodust, under actual field tests, appears to be more efficient 
in killing insects than ordinary nicodust containing the same percent- 
age of "Nicotine Sulfate 40 per cent." Thus in the control of the 
rosy apple aphis, a sulfur-nicodust containing 50 per cent of sulfur, 
6 per cent of "Nicotine Sulfate 40 per cent," and 44 per cent of 
inert material gave far better results than a 6 per cent nicodust. 



Circular 265] plant disease AND PEST CONTROL 89 

The strengths commonly used are 2 per cent nicodust for walnut 
aphis and cherry or pear slug, 5 or 6 per cent for most of the aphids, 
thrips, etc., and a 10 per cent dust for the more resistant aphids such 
as the pea aphis. Nearly all of the hairy caterpillars, such as the tent 
caterpillars, webworms, thistle butterfly larvae, as well as the velvety 
cabbage worms, to which the nicodust adheres readily, are easily killed 
with a 6 per cent dust if applied while the caterpillars are quite young. 
Smooth caterpillars, like cutworms, on the other hand, do not readily 
succumb to any ordinary treatment with the material. Insects which 
are protected with a waxy or cottony material, like the woolly apple 
aphis, the mealy plum louse, mealybugs, etc., are not susceptible to 
nicodust at all, while those which have a wet or slimy covering, like 
the cherry or pear slug, or glandular hairs, like the walnut aphis, are 
easily killed with very weak nicotine contents. 

Recently, machines for mixing and applying the materials at the 
same time have been devised. These promise increased efficiency and 
economy in some large-scale operations. (See University of Calif- 
ornia Bulletin No. 357.) 

Hydrocyanic Acid Gas. — The most effective fumigant in common 
use, but on account of its danger to the operator should if possible 
be used only under expert supervision. The gas is lighter than air, 
diffusing upward very rapidly, hence the danger to occupant of 
upper or adjoining rooms. The danger of explosion and fire from 
the use of carbon bisulfid is practically eliminated with this gas. 

Vacuum fumigation with this and other gases where possible is 
more successful than that in improvised fumigating rooms. 

The gas is generated by adding the cyanid to a solution of sul- 
furic acid. 

The amount of sodium cyanid required for a tightly built room 
is 1% ounces per 100 cubic feet, the chemicals being used in the follow- 
ing proportions: 

Sodium cyanid 1% pounds 

Sulfuric acid 2% pints 

Water 3 pints 

A room, 10 x 16 x 10 feet, contains 1600 cubic feet and would 
require 1% pounds of sodium cyanid, 2% pints (66 ounces by weight) 
of sulfuric acid, and 3 pints of water. The proportions for the chem- 
icals given should not vary, but the amount used per hundred cubic 
feet must be determined according to the tightness of the room. The 
above amount of cyanid may be reduced one-third in a room built 
especially for fumigating purposes, with a corresponding change in 



90 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 

the amounts of acid and water. Twice the above dosage, or even more, 
should be used for buildings of only approximate tightness. 

Liquid hydrocyanic acid gas is now used for citrus orchard fumi- 
gation. For full directions consult the local county agent or horti- 
cultural officers. 

MISCELLANEOUS 

Carbon Tetrachloride. — This may be substituted for carbon disul- 
fid in household fumigation by using it in the same manner and 
slightly increasing the amount used. It is non-inflammable and con- 
sequently safer than carbon disulfid, while its lower toxicity makes it 
safer for the operator. 

Corrosive Sublimate (Bichlorid of Mercury or Mercuric Chlorid). 
— This is a very poisonous substance and is one of the most powerful 
of germicides ; it is employed to some extent in plant disease treatment. 
The usual strength is : 

Formula 28 

Corrosive sublimate 1 ounce 

Water 8 gallons 

Or 1 part to 1000. 

Tablets to make this strength when added to 1 pint of water may 
be obtained at drug stores. Distilled or rain water should be used; 
the solution must not be kept in a metal container. It is also quickly 
spoiled by contact with clay or an organic substance such as the cut 
surfaces of potatoes. 

Another formula is recommended by Mr. C. F. Reimer for dis- 
infecting tools and cuts in pear blight control work. It will probably 
be found superior to Formula 28 for general tree work of this kind. 
It is: 

Formula 28a 

Corrosive sublimate 1 ounce 

Mercuric cyanid 1 ounce 

Water 4 gallons 

Or 1 part of each ingredient to 500. 

Whitewash. 

Formula 29 
(Ordinary Formula) 

Water 2 gallons 

Quicklime 10 pounds 

Add more water after slaking to bring the wash to the desired 
consistency. 



Circular 265] PLANT DISEASE AND PEST CONTROL 91 

A more durable whitewash : 

Formula 30 

Quicklime 5 pounds 

Salt % pound 

Sulfur % pound 

Slake the lime slowly with water and add the salt and sulfur while 
it is boiling. Add enough more water to make a good wash. This is 
good for whitewashing the bodies of trees in the fall. In localities 
where there are deer this whitewash is not recommended, as the deer 
are said to be attracted by the salt it contains and injure the trees. 

Government Whitewash. 

Formula 31 

Quicklime 40 pounds 

Salt 15 pounds 

Rice flour 3 pounds 

Spanish whiting V2 pound 

Glue 1 pound 

Water 5 gallons 

Grafting Wax. — Many different combinations are used for this 
purpose, most of them being various combinations of beeswax and 
resin. The following formula is a good one: 

Formula 32 

Resin 4 pounds 

Beeswax 1 pound 

Linseed oil 1 pint 

The ingredients are all melted and mixed together in a kettle. In 
hot weather use more resin. 

Some use one pound of tallow as a substitute for the linseed oil. 
One ounce of lampblack or one pint of flour is sometimes added. 
Asphaltum is used to some extent as a substitute for resin and bees- 
wax, and, in fact, straight asphaltum is used successfully in some cases 
for grafting wax. 

Carbon Disulfid. — A liquid which evaporates quickly when ex- 
posed to the air, forming a heavy and inflammable vapor of great 
penetrating power. In using the material for fumigation, it is essen- 
tial that it be placed near the top of the chamber in a shallow container 
in order that the heavy vapors as they are given off may thoroughly 
diffuse through the air contained in the space to be fumigated. The 
proper amount to use depends upon the type of room being fumigated 
and ranges from 10 pounds to about 30 pounds to 1000 cubic feet in 



92 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 

ordinary rooms where the walls and floor have not been made especially 
tight. The best results are obtained by doing this work when the 
temperature is above 70° F. 

Carbon disulfid is one of the best agents for destroying ground 
squirrels that have failed to take poisoned grain, or having once sur- 
vived the poison refuse to take it again. It is most effective if used 
during the winter season when the ground is wet. The best methods 
of applying it are by the use of the "waste-ball" and of the "de- 
structor pump." The common waste-ball method is to pour a table- 
spoonful of carbon disulfid on a piece of cotton waste, corncob, horse 
manure, or other absorptive material, and then to throw this as far 
down the hole as possible, closing the opening immediately with earth. 
Exploding the gas with a torch before closing the opening is recom- 
mended where the ground is damp and there is no danger of fire. The 
explosion of gas forms new compounds which are poisonous and may 
diffuse somewhat more rapidly than the vapors of the material. The 
"destructor" pumps the vaporized carbon bisulfid into the burrow, 
and is said to be as effective as exploding the gas. 

Poisoned Barley or Strychnine-coated Barley. — Following is the 
latest government formula for preparing poisoned barley for Calif- 
ornia ground squirrels. 

Formula 33 

Barley (clean grain) 16 quarts 

Strychinine (powdered alkaloid) 1 ounce 

Bicarbonate of soda (baking soda) 1 ounce 

Thin starch paste % pint 

Heavy corn syrup % pint' 

Glycerin 1 tablespoonful 

Saccharin 1/10 ounce 

Mix thoroughly 1 ounce of powdered strychnine (alkaloid) and 
1 ounce of common baking soda. Sift this into % pint of thin, hot 
starch paste and stir to a smooth, creamy mass. (The starch paste 
is made by dissolving 1 heaping tablespoonful of dry gloss starch 
in a little cold water, which is then added to % pint of boiling water ; 
boil and stir constantly until a clear, thin paste is formed.) Add 
14 pint of heavy corn syrup and 1 tablespoonful of glycerin and 
stir thoroughly. Add Vio ounce of saccharine and stir thoroughly. 
Pour this mixture over 16 quarts of clean barley and mix well so that 
each grain is coated. 

Caution. — All containers of poison and all utensils used in thq^ 
preparation of poisons should be kept PLAINLY LABELED and 
OUT OF REACH of children, irresponsible persons, and live stock. 



Circular 265] PLANT DISEASE AND PEST CONTROL 93 

Formula 34 

Poisoned Vegetables for Gophers 

Sweet potatoes, parsnips, or carrots (cut in %" cubes) 4 quarts 

Flour paste *4 pint 

Strychnine alkaloid, powdered ~ % ounce 

Saccharin 1/32 ounce 

SPREADERS 

Spreaders are often added to sprays to give them a more even dis- 
tribution over the surface of the leaves and to prevent them from 
collecting into drops. Some of them also have insecticidal value and 
others act as adhesives. So much is claimed for these materials 
which is not fully warranted that many persons have come to feel 
that none should be recommended. However, the advantages gained 
should not be entirely overlooked, and we include here some of the 
more important substances used for these purposes. 

Casein. — This is a comparatively new material for use as a spreader 
and adhesive in sprays. It is a dry product which readily mixes 
in cold water and is put up in small or large containers. One and 
one-half pounds are sufficient for 200 gallons of the diluted spray. 
Casein is soluble only in alkaline solutions and is therefore worth- 
less in acid insecticides and fungicides which are, however, seldom 
used. 

Flour Paste, Billboard Paste. — These materials are excellent 
spreaders and act as adhesives as well. They may be used with safety 
in all sprays, because they give no chemical reactions. Flour paste 
and certain of the dry billboard and paperhanger 's pastes should be 
mixed in a small quantity of hot water before adding to the spray 
tank. They are somewhat difficult to handle. A specially prepared 
billboard and paperhanger 's paste, known as " steamed paste," is 
already cooked, and as a wet paste mixes readily with cold water. 
It may be obtained in barrel lots or in small quantities from paint and 
paper dealers. The amounts to be used are as follows : 

Flour (cheap grade), 2 to 4 pounds to 200 gallons of dilute spray 

material. 
Dry billboard paste, 2 pounds to 200 gallons of dilute spray 

material. 
Steamed paste, 4 pounds to 200 gallons of dilute spray material. 



94 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION 

Glue. — As a spreader and adhesive, glue has long been used in 
sprays, and, like the flour pastes, may be used in all kinds of materials. 
Two ounces of dry glue dissolved in hot water are sufficient for 200 
gallons of diluted sprays. 

Oil Emulsions and Miscible Oils. — Because of their penetration, 
these materials are often of value in carrying other materials, like 
nicotine. They should be used sparingly, about 2 gallons to 200 
gallons of diluted spraying materials. When so diluted they have 
little value except as spreaders. 

Resin-fish oil soap (see Formula 10a) is often used with Bordeaux 
mixture. It is somewhat tedious to prepare and may now be pur- 
chased ready to use. This is very similar in character to the resin 
wash (see Formula 25). 

Soap. — This is one of the oldest and best known spreaders and is 
often used in sprays for this purpose as well as for an emulsifier and 
insecticide. As a spreader for such materials as arsenate of lead, 
for codling moth, use 4 to 12 pounds of fish oil soap to 200 gallons 
of diluted spray material. 



HEAT AS AN INSECTICIDE 

A temperature of 130° F., as far as records go, if prolonged for 
several hours, will kill all forms of insect life. This temperature 
can readily be obtained in well-built buildings which are connected 
with a steam plant. The first expense of installing radiators is con- 
siderably more than fumigation with chemicals, but after-treatments 
are very much cheaper and without danger to the operators or to the 
contents of the building. 

Higher temperatures of 145° to 180° F. have been reported as 
successful in a much shorter period of time than the first figure men- 
tioned. The desired degree of heat, however, must be obtained 
throughout the entire mass which is being treated, it not being suf- 
ficient to heat the room alone to 145° or more. Small amount of 
provisions or woolen cloths infested with moths may be heated for 
thirty or forty minutes, in the oven of an ordinary cook stove, care 
being taken to avoid scorching heat. A temperature high enough to 
slightly brown a white paper bag will be found about right. The 
use of a smoothing iron just hot enough not to scorch will kill the 
larvae of clothes moths while in the cloth, but other measures must 
be taken to reach the adult insects. 



Circular 265] PLANT DISEASE AND PEST CONTROL 95 



SOIL DISINFECTION 

For the prevention of damping off and of many specific soil-borne 
infections, treatment may be practical in cases such as seedbeds, 
greenhouse soil or where limited amounts of material are to be dealt 
with. Plants at first are slightly retarded, but soon grow with in- 
creased vigor in properly disinfected soils. 

Steam Cooking is generally considered the most effective method 
of soil treatment for the above purposes and various devices have 
been employed for doing the work. A system of 1% i ncn pipes may 
be laid 18 inches apart and 1 foot below the surface. These pipes 
should be perforated on their lower sides with i/^-inch holes at in- 
tervals of 6 inches and should be supplied with steam at a pressure 
of 80 to 150 pounds pressure. The soil should be covered with 
blankets before the steam is admitted, and potatoes buried in different 
places in the soil. After treatment for an hour, the potatoes may be 
examined and if cooked, the treatment may be considered effective. 
The soil may be used in place or may be removed to clean benches 
or beds, using care not to again contaminate it. Benches, frames, 
etc. should be drenched with boiling water or formaldehyde solution 
before use. See below. 

The Inverted-Pan Method consists in admitting steam below an 
inverted galvanized iron pan, furnished with handles for moving, 
and which is pressed down to confine the steam. A size of 6' x 8', 
and 6 inches deep has been recommended. Injurious insects, fungi, 
nematodes and weed seed are destroyed by steam cooking and it has 
been reported in some cases that the cost has not been greater than 
that of weeding untreated soil. 

Surface Firing. — Brush is frequently piled on seedbeds prepared 
for sowing and burned. Seed is sown as soon as possible with a 
minimum stirring of the surface. The effect in this case is very 
superficial. 

Formaldehyde Treatment. — Formaldehyde may be used on seed- 
beds prepared to sow. The soil may be soaked with a solution of 
1 pound of formalin in 6 gallons of water. The soil should be kept 
covered for a day and allowed to stand for a week before sowing. 

Hot Water Treatment. — Considerable benefit may be derived from 
drenching the soil with boiling water. Empty pots, flats, pots with 
soil, and implements may be immersed in boiling water for five 
minutes. 



96 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 



WEED KILLERS, TREE KILLERS 

Salt. — Common salt may be applied on walks or similar places 
where it is desired to prevent the growth of all vegetation. In the 
studies of barberry eradication it was found that 10 pounds of com- 
mon salt poured about the base of the large shrubs was one of the 
surest means of eradication. Soil with which the salt comes in con- 
tact is injured for growing plants. 

Sodium Arsenite. — See p. 73. This is one of the most widely 
used of weed killers. Sprayed on foliage or the soil it is very 
destructive to vegetation. Like common salt, it permanently injures 
soil where applied in considerable quantity. 1 pound of the arsenic in 
10 to 25 gallons of water may be sprayed on soil or foliage. For 
killing trees, use 1 pound to 2 gallons of water, girdle the tree by 
downward strokes of the axe and pour about 1 pint to 1 quart of 
the solution into the cuts. This is a dangerous poison whether to 
handle, to get on fodder, or to inhale its fumes when preparing it. 

Carbon Disulfid. — For killing morning glory, apply in dry soil 
in holes 18 inches deep and 3 feet apart each way. Put 4 ounces of the 
liquid in each hole and cover. This does not permanently injure the 
soil. See also under "Lawns," p. 31. 



Circular 265] 



PLANT DISEASE AND PEST CONTROL 



97 



INDEX 



Acanthoscelides obtectus Say, 13. 

Achemon sphinx moth, 29. 

Actinomyces scabies (Thaxter) Giiss., 
45. 

Aegeria opalescens Hy. Edw., 37. 

Aegeria rutilans H. Edw., 48. 

Aegeria tipuliformis Clerck., 24. 

Angumoise grain moth, 22, 28. 

Alfalfa, 1. 

Alfalfa caterpillar, 2. 

Alkali sulfides, 79. 

Almond, 3. 

Almond mite, 3. 

Ammoniacal solution of copper car- 
bonate, 76. 

Anarsia lineatella Zeller, 37. 

Anasa tristis De Geer, 32. 

Anthraenose (bean), 12. 

Ants, 60. 

Ant Syrup, Government Argentine, 
74. 

Ant syrups, 73. 

AnurapMs roseus Baker, 5. 

Aphids (celery), 17; (chrysanthe- 
mum) 19, (citrus) 21, (grain) 
28, (potato) 45, (rose) 46, (snap- 
dragon) 47. 

Aphis — Artichoke, 11; Bean (bean), 
13, (dahlia) 25; Black cherry, 
18; brassicae Linn., 16; Cabbage, 
16; Green apple (apple), 5, 
(loquat) 31, (pear) 41; Hop, 30; 
Melon (cucumber) 24, (melon) 
32, (spinach) 48; Pear root, 41; 
pomi De Geer, 5; Rosy, 5; 
rumicis Linn., 13 ; Strawberry, 48 ; 
Walnut, 52; Woolly apple, 6. 

Apoplexy (grape), 29. 

Apple, 4. 

Apricot, 7. 

Archips argyrospila Walker, 5. 

Armillaria (almond) 3, (apricot) 7, 
(cherry) 18, (olive) 33, (peach) 
36, (plum, prune) 42, (walnut) 
51. 

Armillaria mellea (Vahl.) Quel., 53. 

Armillaria root rot (citrus) 20, 53. 

Armyworms (alfalfa) 2, (beet) 14, 
(cabbage) 16, (citrus) 21, (corn) 
22, (grain) 28, (grape) 29, 
(onion) 34, (pea) 35, (potato) 
45, (sorghum, etc.) 47, (spinach) 
48, (tomato), 51, 53. 

Arsenate of lead (with nicodust), 
88. 



Arsenic, trioxide, 71. 

Arsenic, White, 71. 

Arsenical dip, Government, 71. 

Arsenicals, 70. 

Artichoke, 10. 

Ascaris lumbricoides Linn., 67. 

Asparagus, 11. 

Aspidiotus hederae Vail., 34. 

Aspergillus niger V. Tiegh., 26. 

Aspidiotus perniciosus Comst., 6. 

Aulacaspis rosae (Bouche), 16. 

Avocado, 11. 

Bacillus amylovorus (Burr.) De T. 
(apple) 4, (loquat) 31, (pear) 39. 

Bacterial gummosis — See Gummosis. 

Bacteriosis (pea), 35. 

Bacterium cerasi Griffin, 7. 

Bacterium citriputiale, 19. 

Bacterium savastanoi E. F. Smith, 33. 

Bacterium tumefaciens S. & T. (bush 
fruits) 15, (grape) 28, 55. 

Barley, 26. 

Bean, 12. 

Bed bugs, 60. 

Beeswax, 91. 

Beet, 13. 

Beetle — Bark (apricot), 10; Dried 
fruit, (date) 25, (prune) 43, 
(raisin) 29; Fruit tree bark (avo- 
cado), 12; Fuller's rose (citrus), 
22, (rose) 47; Olive bark, 34; 
Rose snout, 47; Strawberry flea, 
49; Strawberry leaf, 49. 

Beetles — Darkling ground (tomato), 
51; Flea (cucumber) 23, Hop, 
30, (melon) 32, (potato) 45, 
(spinach) 48, Strawberry, 49, 
(tomato) 51; Leaf (potato), 45; 
Striped cucumber (cucumber), 24, 
(melon) 32; Twelve-spotted cu- 
cumber (cucumber), 24, (dahlia) 
25, (melon) 32. 

Belascarius marginata Rud., 66. 

Bichlorid of mercury, 90. 

Billboard paste, 93. 

Bitter pit (olive), 33, 57. 

Blackberry, 15. 

Black end (pear), 39. 

Black heart (apricot) 7, (potato) 44. 

Black knot (grape), 28. 

Black leaf (pear), 39. 

Black measles (grape), 29. 

Black pit (citrus), 19. 

Black scale (olive) 33, (peach) 37. 

Black scurf (potato), 44. 



98 



UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 



Blapstinus sp., 51. 

Blast (citrus), 19. 

Blight (apple), 4; Bacterial (pea), 
35; (beet) 13; Bud (apricot), 8, 
(camellia) 17; Cane, 15; (celery) 
17; Late (tomato), 50; (pea) 35; 
Peach (apricot), 8, (peach), 36; 
Pear (loquat), 31, (pear) 39; 
Potato late, 44; Twig (apricot), 
9, (walnut) 51; Western (to- 
mato), 50. 

Blue mold (citrus), 20. 

Bluestem, 15. 

Bluestone, 75. 

Bordeaux mixture (average strength), 
74; Commercial, 75; Eesin, 75. 

Bordeaux paste, 74. 

Borer, Branch and twig (apricot), 9, 
(avocado) 12, (fig) 26, (olive) 
33, (peach) 37, (pear) 40, (plum, 
prune), 42. 

Borer, California peach (almond), 3, 
(apricot) 10, (cherry) 18, (peach) 
37, (plum, prune) 42. 

Borer, Flat-headed apple-tree (apple) 
5, (currant, gooseberry) 24, 
(peach) 37, (plum, prune) 43. 

Borer, Imported currant, 24. 

Borer, Nautical, 52. 

Borer, Peach twig (almond) 3, (apri- 
cot) 10, (peach) 37, (plum, 
prune) 43. 

Borer, Potato stalk, 46. 

Borer, Shot hole (apricot) 10, (peach) 
38. 

Borers, Flat-headed, 81. 

Botrytis, 15. 

Botrytis cinerea, 26. 

Bran mash, Citrus, 72; Poison, 72. 

Bromius obscurus (Linn.), 29. 

Broom corn, 47. 

Brown rot (apricot), 8, (peach) 36, 
(plum, prune) 42. 

Brown rot of lemon (citrus) 20, 
(nursery stock) 33. 

Brown streak (potato), 44. 

Bruchus pisorum Linn., 35. 

Bruchophagus funebris How., 2. 

Bryobia praetiosa Koch., 3. 

Bucculatrix thurberiella Busck., 23. 

Bugs, Tule or stink, 62. 

Bush fruits, 15. 

Butterfly, The painted lady, 30. 

Cabbage, 16. 

Calandra granaria Linn., 28. 

Calandra oryzae Linn., 28. 

Caliroa cerasi (Linn.), 19. 

Camellia, 17. 

Canker, Pythiacystis (avocado), 11. 



Cankerworms (apple), 6, (apricot) 

10, (peach) 37, (pear) 40, (plum, 

prune), 42, 54. 
Cantaloupe, 31. 
Carabidae, 54. 

Carbolic acid emulsion, Crude, 86. 
Carbolic acid, Crude, and distillate 

emulsion, 87. 
Carbon disulfid, 28, 90, 91, 96. 
Carbon tetrachloride, 90. 
Carpophilus hemipterus (Linn.), 43. 
Casaba, 31. 
Casein, 93. 

Caterpillar, Celery, 17. 
Caterpillar, Eed-humped (almond), 

3, (apple) 6, (apricot) 10, 

(cherry) 19, (pear) 41, (plum, 

prune) 43, (walnut) 52. 
Caterpillar, Tent (apple) 6, (cherry) 

19, (peach) 38, (plum, prune) 

44, 59. 
Caterpillar, Yellow-necked, 52. 
Cattle (Pests and parasites), 63. 
Celery, 17. 

Centipede, Garden, 11. 
Ceratocystis, 49. 
Cercospora apii Fr., 17. 
Cercospora beticola Saec, 14. 
Cherry, 18. 

Chloridea obsoleta (Fab.), 22. 
Chortophila hyoscyami Panzer, 48. 
Chromaphis juglandicola (Kalt.), 52. 
Chrysanthemum, 19. 
Chrysobothris mali (Horn), 5. 
Chrysomphalus dictyospermi Morgan, 

12. 
Cineraria, 19. 
Citrus fruits, 19. 
Citrus trees (nursery), 32. 
Cladosporium carpophylum Thiim., 9. 
Clover seed chalsis, 2. 
Coal tar creosote dip, 87. 
Coccomyces hiemalis, 18. 
Coccus citricola, Campb., 22. 
Cockroaches, 60. 
Coddling moth (apple), 4, (pear) 41, 

(walnut) 51. 
Cold injury, 55, (rose) 46. 
Colletotrichum lindemuihianum (S. & 

M.) B. & C, 12. 
Combined spraying. — See Spraying. 
Coniothyrium, 15. 
Copper carbonate, 75; Ammoniacal 

solution of, 76; dust, 27. 
Copper compounds, 74. 
Copper sulfate, 75. 
Corn, 22. 

Corn earworms. — See Earworms. 
Corrosive sublimate, 31, 90. 
Corticium vagum B. & C. (bean), 12, 

(beet) 14, (potato) 45. 



Circular 265] 



PLANT DISEASE AND PEST CONTROL 



99 



Coryneum beijerinclcii Oud. (almond), 
3, (apricot) 8, (cherry) 18, 
(peach) 36, (plum, prune), 42. 

Cotton, 23. 

Cottony rot (citrus), 20. 

Coulure (grape), 28. 

Creosote dip, 87. 

Cresylic acid, 87. 

Crioceris asparagi Linn., 11. 

Crown gall (almond), 3, (apricot) 7, 
(bush fruits) 15, (grape) 28, 
(nursery stock) 32, (peach) 36, 
(plum, prune) 42, (walnut) 51, 
55. 

Crown wart (alfalfa), 1. 

Crude oil emulsion, 82. 

Cucumber, 23. 

Curly-leaf (beet), 13. 

Currant, 24. 

Cuscuta sp., 1. 

Cutworms (alfalfa), 2, (beet) 14, 
(cabbage) 16, (citrus) 21, (corn) 
22, (grain) 28, (grape) 29, 
(onion) 34, (pea) 35, (potato) 
45, (sorghum, etc.) 47, 53. 

Cycloconium oleaginum Cast., 33. 

Cydia pomonella (Linn.) (apple), 4, 
(walnut) 51. 

Cylindrosporium, 18. 

Dahlia, 25. 

Damping off (citrus fruits), 20, (to- 
mato) 50, 55. 

Datana ministra Drury, 52. 

Date, 25. 

Deciduous trees (nursery), 32. 

Demodex folliculorum Simon, 66. 

Diabrotica soror Lee, 24. 

Diabrotica trivittata Mann, 24. 

Diarthronomyia hypoqaea (Low.), 19. 

Dictyocaulus ftlaria Rud., 65. 

Dictyocaulus viviparus Bloch., 64. 

Die-back (Cherry), 18, (olive) 33, 57. 

Diplodia zeae (Schw.) Lev., 22. 

Dipylidium caninum Linn., 66. 

Distillate, Straight "tree," 84. 

Distillate emulsion, 86. 

Distillate emulsion, "Tree," 83. 

Distillate emulsion and tobacco ex- 
tract, 85. 

Distillate emulsions, Heavy, 84. 

Distillates, Petroleum, 82. 

Dodder (alfalfa), 1. 

Dogs( pests and parasites), 66. 

Dothiorella qregaria Sacc, 51. 

Downy mildew. — See Mildew. 

Dried fruit beetle. — See Beetle. 

Dropping of fruit (fig), 25. 

Drosophila melanog aster Meigen., 26. 

Dry rot (olive), 33, 57. 

Ear mold (corn), 22. 

Ear ticks, 63. 



Earthworms, 31. 

Earworm, Corn (corn), 22, (cotton) 
23. 

Eccoptog aster rugulosus (Ratz.), 10. 

Eel worm (potato), 45, 56. 

Emulsion, Crude oil, 82. 

Emulsion, Distillate, and tobacco ex- 
tract, 85. 

Emulsion, Kerosene, 83. 

Emulsion, Tree distillate, 83. 

Emulsions, Commercial prepared, 85. 

Emulsions, Heavy distillate, 84. 

Epidiaspis piricola Del G., 41. 

Epochra canadensis Loew., 24. 

Ergot of rye and rye grass, 27. 

Eriophyes erinea Nalepa, 52. 

Eriophyes gracilis (Nalepa), 16. 

Eriophyes pyri (Pagen), 41. 

Eriosoma languinosa (Hartig), 41. 

Eriosoma lanigera (Hausm.), 6. 

Erysiphe dehor earum D. C, 23. 

Erysiphe polygoni D. C. (bean) 12, 
(pea) 35. 

Erysiphe sp., 25. 

Erythroneura comes (Say), 29. 

Eurymetopon bicolor Horn, 51. 

Eurymus eurytheme (Boisd.), 2. 

Eutettix tenella Baker, 13. 

Exanthema (olive), 33, 57. 

Exoascus cerasi Fuckel, 18. 

Exoascus deformans Fcl., 36. 

Exoascus pruni Fcl., 42. 

Failure of flower buds to open (apri- 
cot), 9. 

Failure to grow, etc. (nursery stock), 
32. 

Ferns, 25. 

Fig, 25. 

Fish oil, 86; Fish oil soap, 86. 

Flea beetles. — See Beetles. 

Fleas, 61, 66. 

Flies, 61. 

Flour paste, 93. 

Flour paste, billboard paste, 93. 

Flo.ur paste (spreader), 93. 

Formaldehyde treatment (soil), 95. 

Formulas and descriptions of mate- 
rials, 70. 

EranTcliniella tritici (Fitch), 38. 

Frost injury, 55. 

Frost scabs (apricot), 9. 

Fruit cracking (apricot), 9. 

Fruit fly, Currant and gooseberry, 24. 

Fruit tree leaf roller (apple), 5. 

Fruit spot, 8. 

Fruit tree roller, 41. 

Fuller's rose beetle (citrus), 22 (rose) 
47. 

Fusarium, 55. 

Fusarium conglutinans Woll., 16. 

Fusarium malli Taub., 34. 



100 



UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 



Fusarium sp. (bean), 12, (beet) 14, 
(corn) 22, (melon) 32, (potato) 
45, (sweet potato) 50, (tomato) 
50. 

Fusicladium (apple), 4, (pear) 40. 

Fusicladium eryobotryae Sciala, 31. 

Fly, Fruit,— See Fruit fly. 

Fly, Gall.— See Gall fly. 

Fly, Pomace or vinegar, 26. 

Gall fly, Chrysanthemum, 19. 

Garden nematode (potato), 45. 

Glue, 94. 

Glycerine (in pear blight disinfect- 
ant), 39. 

Gooseberry, 24. 

Gophers, 68. 

Government whitewash, 91. 

Grafting wax, 91. 

Grain, 26. 

Grape, 28. 

Grapefruit, 19. 

Grasshoppers (alfalfa), 2, (beet) 14, 
(corn) 23, (grain) 28, (grape) 
30, (potato) 45, (sorghum, etc.) 
47, (spinach) 48, (tomato) 51,56. 

Green mold (citrus), 20. 

Green rot (apricot), 9. 

Ground squirrels, 67. 

Gumming twig blight, 8. 

Gummosis (cherry), 18, (citrus) 20, 
56. 

Gummosis, Bacterial, 7. 

Gymnoconia inter stitialis (Schlect.) 
Lagerh., 15. 

Haematobia serrata B. D., 63. 

Haltica ignita Illiger, 49. 

Hartigia cressoni (Kirby), 15. 

Heat as an insecticide, 94. 

Heliothrips fasciatus Perg. (avocado), 
12, (bean) 13. 

Heliothrips haemorrhoidalis Bouche, 
12. 

Hemerocampa vetusta (Boisd.), 6. 

Heterodera radicicola Greef. (beet), 
14, 56. 

Heterodera schaclitii Schmidt (beet), 
14, 56. 

Hollyhock, 30. 

Hop, 30. 

Hoplocampa coolcei (Clarke), 18. 

Horn flies, 63. 

Horntail, Raspberry (bush fruits), 15, 
(rose) 47. 

Hot water treatment (soils, pots, 
etc.), 95. 

Household pests and animal parasites, 
60. 

Hyalopterus arundinis (Fabr.), 43. 

Hydrocyanic acid gas (grain), 28, 
(formulas, etc), 89. 

Hylemyia antiqua Meig., 34. 

Hypoderma lineata de Villers, 64. 



Ichneumonidae, 54. 

Insects, Venemous, 69. 

Inverted pan method (soil steriliza- 
tion), 95. 

Jelly end (potato), 44. 

June drop (citrus), 21. 

Knot, Olive, 33. 

Kerosene, 82. 

Kerosene emulsion, 83. 

Lawns, 31. 

Lead arsenate, Acid, 70. 

Lead arsenate, Basic, 70. 

Leaf and fruit spot (cherry), 18. 

Leaf curl (cherry), 18, (peach) 36. 

Leaf hopper (beet), see Curly leaf, 
(grape) 29. 

Leaf miner (chrysanthemum), 19, 
(cineraria) 19. 

Leaf miner, Beet or spinach (beet), 
14, (spinach) 48. 

Leaf perforator, Cotton, 23. 

Leaf roller, Fruit tree (apple), 5, 
(apricot) 10, (plum, prune) 43. 

Leaf spot (alfalfa), 2, (beet) 14, 
(bush fruits) 15, (cherry) 18, 
(plum, prune) 42, (strawberry) 
48. 

Leak (potato), 44. 

Lecanium cerasorum Ckll., 52. 

Lecanium corni Bouche, 9. 

Lecanium pruinosum Coq., 52. 

Lemon, 19. 

Leperi'sinus californicus Swaine, 34. 

Lepidosaphes ficus (Sign.), 26. 

Lepidosaphes ulmi (Linn.), 6. 

Leptosphaeria coniothyrium Sacc, 15. 

Lice, 67. 

Lice, Biting, 63. 

Lice, Sucking, 63. 

Lime-sulfur dip, 79. 

Lime-sulfur, Dry, 79. 

Lime-sulfur solution, 78. 

Lime-sulfur solution, Commercial, 78. 

Lime-sulfur solution, Homemade, 78. 

Lime-sulfur wash, Self-boiled, 78. 

Lime water (for wireworms), 31. 

Little leaf (grape), 29, (peach) 36, 
57. 

Loganberry, 15. 

Loquat, 31. 

Lousej Mealy plum, 43. 

Lungworms (cattle), 64, (sheep), 65. 

Macrosiphum pisi (Kalt.), 35. 

Macrosiphum rosae (Linn.), 46. 

Maggot, Head, 65. 

Maggot, Onion, 34. 

Maggot, Wool, 65. 

Mange, 66, 67. 

Mange, Demodectic, 66, 67. 

Mange, Follicular, 66. 

Margaropus annulatus Say, 64. 



Circular 265] 



PLANT DISEASE AND PEST CONTROL 



101 



Mealy bug (citrus), 22, (grape) 30, 
Baker's, 40. 

Melaxuma (walnut), 51. 

Melon, 31. 

Mercuric chlorid, 90. 

Mercuric cyanide, 90. 

Mildew (apple), 4, (bean) 12, (cu- 
cumber) 23, (currant, goose- 
berry) 24, (dahlia) 25, (grape) 

29, (pea) 35, (rose) 46. 
Mildew, Downy (alfalfa), 1, (beet) 

14, (onion) 34, (pea) 35. 

Mildew, Powdery (pea), 35, (peach) 
36. 

Miscellaneous (materials and formu- 
las), 90. 

Miscible oil, 86. 

Miscible oils, 85, (as spreaders) 94. 

Mite, Almond (almond), 3, (plum, 
prune) 44. 

Mite, Blackberry, 16. 

Mite, European red (citrus), 21. 

Mite, Peach rust, 37. 

Mite, Pear leaf blister, 41. 

Mite, Two-spotted (bean), 13, (citrus) 
21, (cucumber) 24, (currant, 
gooseberry) 24, (hop) 31, (straw- 
berry) 49, (walnut) 52. 

Mite, Walnut blister, 52. 

Mites, Grain, 28. 

Mold, Ear (corn), 22. 

Mold, Fruit, 15. 

Mold, Gray (strawberry), 48. 

Monilia blossom blight, 8. 

Monilia brown rot, 8. 

Monilia fructigena, 8. 

Monilia rot of ripe fruit, 8. 

Monilochaetes infuscans E. & H.. 49. 

Mosquitoes, 62. 

Moth, Angumoise grain, 28, 

Moth, Artichoke plume, 10. 

Moth, Clothes, 61. 

Moth, Coddling. — See Coddling moth. 

Moth, Indian meal (date), 25, (raisin) 

30, (prune) 43, (walnut) 52. 
Moth, Potato tuber, 46. 

Moth, Strawberry crown, 48. 

Moth, Tussock, 6, 44. 

Mottled leaf (citrus), 21, 57. 

Mycosphaerella fragariae (Tul.) Linn., 
48. 

Mycosphaerella pinodes Berk. & Blox., 
35. 

Myzaphis rosarum (Walk.), 46. 

Myzus oraggii Gill., 11. 

Myzus cerasi Fabr., 18. 

Myzus fragaefolii Ckll., 48. 

Nematode (melon), 32, (nursery 
stock) 32, (peach) 36, 56. 

Nematode, Garden (bean) 13, (cu- 
cumber) 24, (potato) 45, (to- 
mato) 51 



Nematodes (beet), 14, (fig), 26. 

Nicodust and combinations, 88. 

Nicotine sulfate, 85, 86, 87, 88. 

Nitrate of soda (for weeds), 31. 

Notolophus antiqua (Linn.), 6. 

Nursery stock, 32. 

Oak fungus, 53. 

Oat, 33. 

Oats, 26. 

Oats (sensitive to bluestone), 27. 

Obscure diseases (grape), 29. 

Oestrus ovis Linn., 65. 

Oidium, 46. 

Oil emulsions (as spreaders), 94. 

Olive, 33. 

Olive knot, 33. 

Onion, 34. 

Oospora, 45. 

Orange, 19. 

Ornithodorus megnini Duges, 63. 

Otiorhynchus rugifrons Gyll., 49. 

Oyster shell scale. — See scale. 

Pantomorus fulleri (Horn), 22. 

Papilio zolicaon Boisd., 17. 

Para-dichloroben*ene, 80. 

Paratetranychus pilosus C. & F., 21. 

Paria canella (Fabr.), 49. 

Parlatoria olanchardi (Targ.), 25. 

Paste, Dry billboard, 88. 

Paste, Flour and billboard, 93. 

P D B, 80. 

Pea, 35. 

Peach, 36. 

Peach blight. — See blight. 

Peach twig borer. — See borer. 

Peacock spot (olive), 33. 

Pear, 39. 

Pear blight. — See blight. 

Penicillium sps. (citrus), 20. 

Peritymbia vitifoliae (Fitch), 30. 

Peronospora schactii Fcl., 14. 

Peronospora schleideni Ung., 34. 

Peronospora trifoliorum De Bary (al- 
falfa) 1, (pea) 35. 

Petroleum, Crude, 81. 

Petroleum distillates, 82. 

Phoenico coccus marlatti Ckll., 25. 

Pholus achemon (Drury), 29. 

Phorbia brassicae Bouche, 17. 

Phorodon humuli (Schr.), 30. 

Phyllocoptes cornutus Banks, 37. 

Phylloxera, Grape, 30. 

Physiological diseases (plum, prune), 
42, 57. 

Phytomyta chrysanthemi Kow., 19. 

Phytopthora infestans (Mont.) De 
Bary (potato), 44, (tomato) 50. 

Phthorimaea operculella (Zeller), 46. 

Pink root (onion), 34. 

Plant lice (ferns), 25. 

Platyptilia carduidactyla (Eiley), 10. 

Plenodomus destruens Harter, 49. 



102 



UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 



Plodia interpunctella Hiibn., 43. 

Plum, 42. 

Plum pockets, 42. 

Polycaon confertus Lee. (apricot), 9, 
(olive) 33, (peach) 37. 

Poison baits, substitutes in, 72. 

Poisoned barley, 92. 

Poisoned vegetables for gophers, 93. 

Polystictis versicolor (L.) Fr., 4. 

Pontia rapae (Linn.), 16. 

Potato, 44. 

Powdery mildew. — See mildew. 

Protoparce quinquemaculata Haw., 51. 

Protoparce sexta Joh., 51. 

Prune, 42. 

Pruning cuts and wounds, Treatment 
of, 58. 

Pseudococcus (citrus), 22. 

Pseudococcus odkeri Essig (grape), 
30, (pear) 40. 

Pseudococcus maritimus Ehr. (grape), 
30, (pear) 40. 

Pseudomonas juglandis Pierce, 51. 

Pseudomonas oleae, 33. 

Pseudomonas pisi Sack., 35. 

Pseudopeziza medicaginus (Lib.) 
Sacc, 2. 

Psoroptes communis var. ovis Hering, 
65. 

Psylliodes punctulata Mels., 30. 

Puccinia antirrhini D. & H., 47. 

Puccinia asparagi D. C, 11. 

Puccinia chrysanthemi Roze., 19. 

Puccinia malvacearum Mont., 30. 

Puccinia pruni (almond), 3, (apricot) 
9, (peach) 36, (plum, prune), 42. 

Puccinia sps., 26. 

Pumpkin, 31. 

Pythiacystis citrophthora S. & S. (avo- 
cado), 11, (citrus) 20, (nursery 
stock) 33. 

Pythiacystis canker (nursery stock), 
33. 

Pythiacystis rot (citrus), 20. 

Pythium (potato), 44, 55. 

Rabbits, 69. 

Raisin, 28. 

Ramularia, 48. 

Raspberry, 15. 

Rats, 69. 

Red humped caterpillar. — See cater- 
pillar. 

Red specking (apricot), 9. 

Red spider (bean), 13, (cucumber) 
24, (currant) 24, (date), 25, 
(hop) 31, (peach) 38, (plum, 
prune) 44. 

Red spider, Citrus, 43. 

Red spider, Common, 44. 

Red spider or almond mite, 3, 44. 

Resin, 91. 

Resin-Bordeaux mixture, 75. 



Resin fish oil soap (as spreader), 94. 

Resin wash, 86. 

Rhuoctonia (bean), 12, (beet) 14, 
(potato) 44, 55. 

Rhizopus, 44. 

Rhizopus nigricans Ehr., 49. 

Rhopalosiphum persicae (Sulz.), 17. 

Rhynchites licolor Fabr., 47. 

Root maggot, Cabbage, 17. 

Root rot, Armillaria, 53. 

Root rot, Seedling, 14. 

Root worm, California grape, 29. 

Rose, 46. 

Rosette, 57. 

Rot, Black (sweet potato), 49. 

Rot, Blossom end (melon), 31, (to- 
mato) 50, 57. 

Rot, Botrytis (strawberry), 48. 

Rot, Dry (potato), 45, 57. 

Rot, Foot (sweet potato), 49. 

Rot, Late (potato), 44, (tomato) 50. 

Rot, Leaf and stem (strawberry), 48. 

Rot, Soft (potato), 44, (sweet po- 
tato) 49. 

Rot, Stem (sweet potato), 50. 

Roundworms (dogs), 66, (swine) 67. 

Rust (alfalfa), 2, (almond) 3, (apri- 
cot) 9, (asparagus) 11, (bean) 12, 
(beet) 14, (chrysanthemum) 19, 
(grain) 26, (hollyhock) 30, 
(peach) 36, (plum, prune) 42, 
(snapdragon) 47. 

Rust, Orange (bush fruits), 15. 

Rye and Rye grass, 27. 

Saissetia oleae (Bern.), 9, 33. 

Salt (as tree killer), 96. 

San Jose scale. — See scale. 

Sappy bark (apple), 4. 

Sarcoptes scaoiei var, canis Linn., 66. 

Sawfly, Cherry fruit (cherry), 18, 
(plum, prune) 43. 

Scab (apple), 4, (apricot) 9, (loquat) 
31, (pear) 40, (potato) 45. 

Scab (sheep), 65. 

Scabies (dog), 66, (swine) 67. 

Scale, Black (apricot), 9, (ferns) 25, 
(plum, prune) 42. 

Scale, Brown apricot (apricot), 9, 
(peach) 37, (plum, prune) 42. 

Scale, Cherry or calico (walnut), 52. 

Scale, Date palm, 25. 

Scale, Frosted, 52. 

Scale, insects (citrus), 22. 

Scale, Italian pear (pear), 41, (plum, 
prune) 43. 

Scale, Ivy or oleander (olive), 34. 

Scale, Marlatt, 25. 

Scale, Mediterranean fig, 26. 

Scale, Oyster shell (apple), 6. 

Scale, Rose (bush fruits), 16, (rose) 
47. 



Circular 265] 



PLANT DISEASE AND PEST CONTROL 



103 



Scale, San Jose (almond), 3, (apple) 

6, (currant, gooseberry) 24, (lo- 

quat) 31, (peach) 38, (pear) 41, 

(plum, prune) 44. 
Scale, Spanish red, 12. 
Scales, brown apricot and other soft 

(pear), 40. 
Scaly bark (citrus), 21. 
Schuura concinna S. & H., 43. 
Scirtothrips citri (Moult.), 21. 
Sclerotinia cinerea (Bon.) Schrot. 

(apricot), 8, (peach) 36. 
Sclerotinia fructigena, 8. 
Sclerotinia libertiana Fcl. (almond), 

2, (apricot) 9, (citrus) 20, (fig) 

26. 
Scullions (onion), 34. 
Scurf (sweet potato), 49. 
Scutigerella calif ornica (Woodw.), 11 
Septoria rubi West, 15. 
Scptoria petroseleni Desm., 17. 
Sheep (pests and parasites), 65. 
Shot hole (almond), 3, (apricot) 8. 
Silver fish moth, 62. 
Siphocoryne capreae (Fab.), 17. 
Sitotroga cerealla Oliv., 28. 
Slug, Cherry (cherry), 19. 
Slug, Cherry or pear (pear), 40. 
Slugs, 57. 

Smut (fig), 26, (grain) 26. 
Smut, Boil or common (corn), 22. 
Smut, Head (sorghum, etc.), 47. 
Smut, Kernel (grain), 27, (sorghum, 

etc.) 47. 
Smuts, Loose (grain), 27. 
Snails, 57. 
Snapdragon, 47. 
Soap (as spreader), 94. 
Soap, Hard, 83. 
Soap, Liquid, 83. 
Sodium arsenite, 72. 
Sodium arsenite (as tree killer), 96. 
Sodium cyanid, 89. 
Soil disinfection, 95. 
Soil injury (avocado), 12. 
Sorghum, 47. 
Sorghums and Sudan grass, Kernel 

smut of, 27, 47. 
Sour sap (almond), 3, (apricot) 7, 

(cherry) 18, (plum, prune) 42, 57. 
Souring (fig), 26. 
Sow bugs, 62. 
Sphacelotheca reiliana (Kiihn.) Clint., 

47. 
Sphacelotheca sorghi (Lk.) CI., 47. 
Sphaeronema fimoriatum (E. & H.) 

Sacc, 49. 
Sphaerotheca humuli (D. C.) Burr., 46. 
Sphaerotheca leucotricha (E. & E.) 

Salm., 4. 
Sphaerotheca mors-uvae (Schw.) B. & 

C, 24. 



Sphaerotheca oxyacanthae (De C.) De 

B, 4. 
Sphaerotheca pannosa (Wallr.) Lev., 

46. 
Sphaerotheca pannosa var. persicae 

(Wallr.) Lev., 36. 
Sphinx moth, Achemon, 29. 
Spiders, 69. 
Spinach, 48. 
Splitting (fig), 26. 
Spot (pea), 35. 
Spraying, Combined (almond, 4, 

(apple) 6, (apricot) 10, (currant, 

gooseberry) 24, (peach) 39, 

(pear) 42, (plum, prune) 44, 

(potato) 46, (rose) 47. 
Spreaders, 93. 
Squash, 31. 
Squash bug, 32. 
Squirrels, Ground, 67. 
Steam cooking (soil), 95. 
Stem rot (alfalfa), 2, (bean) 12. 
Sterigmatocystis ficum (Reich.) Henn., 

26. 
Strawberry, 48. 
Strychnine-coated barley, 92. 
Sudan grass, 47. 

Sudan grass, Kernel smut of, 27, 47. 
Sulfides, Alkali, 79. 
Sulfur and sulfur compounds, 76. 
Sulfur, Dry, 76. 
Sulfur-nicodust, 88. 
Sulfur pastes, 77. 
Sulfurs, Wettable, 77. 
Sunburn, 59. 

Surface firing (soil disinfection), 95. 
Sweet potato, 49. 
Swine (pests and parasites), 67. 
Taeniothrips inconsequent Uzel., 41. 
Tapeworms, 66. 

Tent caterpillars. — See caterpillars. 
Tetranychus oimaculatus Harvey, 21. 
Tetranychus telarius Linn, (bean), 

13, (currant, gooseberry) 24, 

(plum, prune) 44, (strawberrv) 

49. 
Thrips, Bean (avocado), 12, (bean) 

13, (cotton) 23. 
Thrips, Citrus, 21. 
Thrips, Greenhouse (avocado), 12. 
Thrips, Onion, 34. 
Thrips, Pear (cherry) 19, (pear) 41, 

(plum, prune) 43. 
Thrips taoaci Lind., 34. 
Thrips, Wheat (peach), 38. 
Ticks, 64. 
Tilletia sps., 26. 
Tobacco, 50. 
Tobacco dust, 88. 
Tobacco extract, 85. 
Tobacco preparations, 87. 
Tomato, 50. 



UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 



Toxascaris limbata R. & H., 66. 
Transchelia punctata (Pers.) Arth. 

(almond) 3, (apricot) 9, (peach) 

36, (plum, prune) 42. 
"Tree" distillate, 83, 84. 
Tree killers, 96. 
Trichobaris trinotata Say, 46. 
Trichodectes scalarius Nitzsch., 63. 
Tuberculosis (olive), 33. 
Tussock moths (apple), 6, 44. 
Tyroglyphus sps., 28. 
Uncinula necator (Schw.) Burr., 29. 
Uncinula spiralis B. & C, 29. 
Unfruitfulness (almond), 3, (apricot) 

9, (plum, prune) 42. 
Uromyces appendiculatus (Per s.) 

Link., 12. 
Uromyces oetae (Pers.) Kiihn., 14. 
Uromyces striatus Schr., 2. 
Urophlyctis alfalfae (Lag.) Magn., 1. 
Ustilago sps., 26. 
Ustilago zeae (Beckm.) Ung., 22. 
Vacuum fumigation, 89. 
Vanessa caryae Hiibn., 30. 
Venturia inequalis (Cke.) Wint., 4. 
Venturia pyrina Aderh., 40. 
Verticillium caulophagus (Law.), 15. 
Walnut, 51. 
Warbles, 64. 

Water injury (avocado), 12. 
Watermelon, 31. 



Wax, Grafting, 91. 

Weeds (lawns), 31. 

Weed killers, 96. 

Weevil — Bean, 13; Granary, 28; 
Granary and rice, 23, 47; Pea, 
35; Rice, 28; Strawberry root, 
49. 

Wettable sulfurs, 77. 

Wheat, 26. 

Whitewash, 90, 91. 

Whitewash, Government, 91. 

Wilt (alfalfa), 2, (bean) 12, (cab- 
bage) 16, (melon) 32, (potato) 
45, (sweet potato) 50, (tomato) 
50. 

Winter injury, 57. 

Winter killing (walnut), 51. 

Wireworms (bean), 13, (beet) 14, 
(corn) 23, (lawns) 31, (onions) 
34, (potato) 46, 59. 

Wood decay (apricot), 7, (cherry) 
18, (citrus) 20, (olive) 33, 
(peach) 36, (plum, prune) 42, 
(walnut) 51. 

Wood decay prevention, 58. 

Worm, Cabbage, 16; Tobacco, 51; 
Tomato, 51. 

Worms, Tomato and tobacco, 46. 

Xyleborus xylographus Say, 10. 

Xylotrechus nauticus Mann, 52. 

Yellows (cabbage), 16. 

Zinc arsenite, 71.